Remove :api: tag that has leaked on the doc directly [ci skip]

Currently `:api:` tag has leaked on the doc directly since RDoc doesn't
support `:api:` tag directive.

http://api.rubyonrails.org/v5.1/classes/AbstractController/Rendering.html

So `:api: private` doesn't work as expected. We are using `:nodoc:` for
the purpose.

Related #13989.

actionpack/lib/abstract_controller/base.rb

@@ -180,8 +180,6 @@ module AbstractController
       #
       # ==== Parameters
       # * <tt>name</tt> - The name of an action to be tested
-      #
-      # :api: private
       def action_method?(name)
         self.class.action_methods.include?(name)
       end

actionpack/lib/abstract_controller/rendering.rb

@@ -20,7 +20,6 @@ module AbstractController
 
     # Normalizes arguments, options and then delegates render_to_body and
     # sticks the result in <tt>self.response_body</tt>.
-    # :api: public
     def render(*args, &block)
       options = _normalize_render(*args, &block)
       rendered_body = render_to_body(options)
@@ -42,19 +41,16 @@ module AbstractController
     # (as ActionController extends it to be anything that
     # responds to the method each), this method needs to be
     # overridden in order to still return a string.
-    # :api: plugin
     def render_to_string(*args, &block)
       options = _normalize_render(*args, &block)
       render_to_body(options)
     end
 
     # Performs the actual template rendering.
-    # :api: public
     def render_to_body(options = {})
     end
 
-    # Returns Content-Type of rendered content
-    # :api: public
+    # Returns Content-Type of rendered content.
     def rendered_format
       Mime[:text]
     end
@@ -65,7 +61,6 @@ module AbstractController
 
     # This method should return a hash with assigns.
     # You can overwrite this configuration per controller.
-    # :api: public
     def view_assigns
       protected_vars = _protected_ivars
       variables      = instance_variables
@@ -79,7 +74,6 @@ module AbstractController
     # Normalize args by converting <tt>render "foo"</tt> to
     # <tt>render :action => "foo"</tt> and <tt>render "foo/bar"</tt> to
     # <tt>render :file => "foo/bar"</tt>.
-    # :api: plugin
     def _normalize_args(action = nil, options = {})
       if action.respond_to?(:permitted?)
         if action.permitted?
@@ -95,20 +89,17 @@ module AbstractController
     end
 
     # Normalize options.
-    # :api: plugin
     def _normalize_options(options)
       options
     end
 
     # Process extra options.
-    # :api: plugin
     def _process_options(options)
       options
     end
 
     # Process the rendered format.
-    # :api: private
-    def _process_format(format)
+    def _process_format(format) # :nodoc:
     end
 
     def _process_variant(options)
@@ -121,8 +112,7 @@ module AbstractController
     end
 
     # Normalize args and options.
-    # :api: private
-    def _normalize_render(*args, &block)
+    def _normalize_render(*args, &block) # :nodoc:
       options = _normalize_args(*args, &block)
       _process_variant(options)
       _normalize_options(options)

actionpack/lib/action_controller/metal/instrumentation.rb

@@ -83,15 +83,12 @@ module ActionController
     #   def cleanup_view_runtime
     #     super - time_taken_in_something_expensive
     #   end
-    #
-    # :api: plugin
     def cleanup_view_runtime
       yield
     end
 
     # Every time after an action is processed, this method is invoked
     # with the payload, so you can add more information.
-    # :api: plugin
     def append_info_to_payload(payload)
       payload[:view_runtime] = view_runtime
     end
@@ -100,7 +97,6 @@ module ActionController
       # A hook which allows other frameworks to log what happened during
       # controller process action. This method should return an array
       # with the messages to be added.
-      # :api: plugin
       def log_process_action(payload) #:nodoc:
         messages, view_runtime = [], payload[:view_runtime]
         messages << ("Views: %.1fms" % view_runtime.to_f) if view_runtime

actionpack/test/controller/new_base/base_test.rb

@@ -47,7 +47,6 @@ module Dispatching
   end
 
   class BaseTest < Rack::TestCase
-    # :api: plugin
     test "simple dispatching" do
       get "/dispatching/simple/index"
 
@@ -56,14 +55,12 @@ module Dispatching
       assert_content_type "text/plain; charset=utf-8"
     end
 
-    # :api: plugin
     test "directly modifying response body" do
       get "/dispatching/simple/modify_response_body"
 
       assert_body "success"
     end
 
-    # :api: plugin
     test "directly modifying response body twice" do
       get "/dispatching/simple/modify_response_body_twice"
 

actionview/lib/action_view/context.rb

@@ -19,7 +19,6 @@ module ActionView
     attr_accessor :output_buffer, :view_flow
 
     # Prepares the context by setting the appropriate instance variables.
-    # :api: plugin
     def _prepare_context
       @view_flow     = OutputFlow.new
       @output_buffer = nil
@@ -29,7 +28,6 @@ module ActionView
     # Encapsulates the interaction with the view flow so it
     # returns the correct buffer on +yield+. This is usually
     # overwritten by helpers to add more behavior.
-    # :api: plugin
     def _layout_for(name = nil)
       name ||= :layout
       view_flow.get(name).html_safe

actionview/lib/action_view/rendering.rb

@@ -75,8 +75,7 @@ module ActionView
     end
 
     # Returns an object that is able to render templates.
-    # :api: private
-    def view_renderer
+    def view_renderer # :nodoc:
       @_view_renderer ||= ActionView::Renderer.new(lookup_context)
     end
 
@@ -92,7 +91,6 @@ module ActionView
     private
 
       # Find and render a template based on the options given.
-      # :api: private
       def _render_template(options)
         variant = options.delete(:variant)
         assigns = options.delete(:assigns)
@@ -114,7 +112,6 @@ module ActionView
 
       # Normalize args by converting render "foo" to render :action => "foo" and
       # render "foo/bar" to render :template => "foo/bar".
-      # :api: private
       def _normalize_args(action = nil, options = {})
         options = super(action, options)
         case action
@@ -137,7 +134,6 @@ module ActionView
       end
 
       # Normalize options.
-      # :api: private
       def _normalize_options(options)
         options = super(options)
         if options[:partial] == true