fix(rubocop): Remove nested if inside else Style/IfInsideElse [ci skip]

Rakefile

@@ -24,15 +24,13 @@ task :default do
   if Tests::CurrentBundle.instance.appraisal_in_use?
     sh 'rake spec:unit --trace'
     sh 'rake spec:acceptance --trace'
-  else
-    if ENV['CI']
+  elsif ENV['CI']
     exec 'appraisal install && appraisal rake --trace'
   else
     appraisal = Tests::CurrentBundle.instance.latest_appraisal
     exec "appraisal install && appraisal #{appraisal} rake --trace"
   end
 end
-end
 
 namespace :appraisal do
   task :list do

lib/shoulda/matchers/active_model/allow_mass_assignment_of_matcher.rb

@@ -90,15 +90,13 @@ module Shoulda
           if attr_mass_assignable?
             if whitelisting?
               @failure_message_when_negated = "#{@attribute} was made accessible"
-            else
-              if protected_attributes.empty?
+            elsif protected_attributes.empty?
               @failure_message_when_negated = 'no attributes were protected'
             else
               @failure_message_when_negated = "#{class_name} is protecting " <<
                 "#{protected_attributes.to_a.to_sentence}, " <<
                 "but not #{@attribute}."
             end
-            end
             true
           else
             if whitelisting?

lib/shoulda/matchers/active_record/serialize_matcher.rb

@@ -141,14 +141,12 @@ module Shoulda
             klass = serialization_coder
             if klass == @options[:type]
               true
-            else
-              if klass.respond_to?(:object_class) && klass.object_class == @options[:type]
+            elsif klass.respond_to?(:object_class) && klass.object_class == @options[:type]
               true
             else
               @missing = ":#{@name} should be a type of #{@options[:type]}"
               false
             end
-            end
           else
             true
           end

lib/shoulda/matchers/active_record/validate_uniqueness_of_matcher.rb

@@ -952,8 +952,7 @@ module Shoulda
             end
 
             prefix << ', and saving it as the existing record, then'
-          else
-            if attribute_setter_for_existing_record
+          elsif attribute_setter_for_existing_record
             prefix << "Given an existing #{model.name},"
             prefix << ' after setting '
             prefix << description_for_attribute_setter(
@@ -968,7 +967,6 @@ module Shoulda
             )
             prefix << ', after'
           end
-          end
 
           prefix << " making a new #{model.name} and setting "