Remove errors module

Actually, I changed my mind. dry/core/errors is explicitly required in
dry/core so autoloading shouldn't be needed. Something else is causing
an error in my app.
But I kept the Error postfix.

docsite/source/classes/class-attributes.html.md

@@ -16,7 +16,7 @@ class ExtraClass
 end
 
 # example with inheritance and type checking
-# setting up an invalid value will raise Dry::Core::Errors::InvalidClassAttributeValueError
+# setting up an invalid value will raise Dry::Core::InvalidClassAttributeValueError
 
 class MyClass
   extend Dry::Core::ClassAttributes

lib/dry/core/class_attributes.rb

@@ -81,7 +81,7 @@ module Dry
               elsif type === value # rubocop:disable Style/CaseEquality
                 instance_variable_set(ivar, coerce.call(value))
               else
-                raise Errors::InvalidClassAttributeValueError.new(name, value)
+                raise InvalidClassAttributeValueError.new(name, value)
               end
             end
           end

lib/dry/core/errors.rb

@@ -2,13 +2,11 @@
 
 module Dry
   module Core
-    module Errors
-      class InvalidClassAttributeValueError < StandardError
-        def initialize(name, value)
-          super(
-            "Value #{value.inspect} is invalid for class attribute #{name.inspect}"
-          )
-        end
+    class InvalidClassAttributeValueError < StandardError
+      def initialize(name, value)
+        super(
+          "Value #{value.inspect} is invalid for class attribute #{name.inspect}"
+        )
       end
     end
   end

spec/dry/core/class_attributes_spec.rb

@@ -65,7 +65,7 @@ RSpec.describe "Class Macros" do
         expect {
           klass.one 1
         }.to raise_error(
-          Dry::Core::Errors::InvalidClassAttributeValueError,
+          Dry::Core::InvalidClassAttributeValueError,
           "Value 1 is invalid for class attribute :one"
         )
       end
@@ -90,7 +90,7 @@ RSpec.describe "Class Macros" do
       it "raises InvalidClassAttributeValueError when invalid value is pass" do
         expect {
           klass.one 1
-        }.to raise_error(Dry::Core::Errors::InvalidClassAttributeValueError)
+        }.to raise_error(Dry::Core::InvalidClassAttributeValueError)
       end
     end
   end