Merge pull request #15751 from aditya-kapoor/correct-serialization-doc

[ci skip] correct doc for serialization in accordance with API Doc Guide

activemodel/lib/active_model/serialization.rb

@@ -4,7 +4,7 @@
 module ActiveModel
   # == Active \Model \Serialization
   #
-  # Provides a basic serialization to a serializable_hash for your object.
+  # Provides a basic serialization to a serializable_hash for your objects.
   #
   # A minimal implementation could be:
   #
@@ -25,16 +25,16 @@ module ActiveModel
   #   person.name = "Bob"
   #   person.serializable_hash   # => {"name"=>"Bob"}
   #
-  # You need to declare an attributes hash which contains the attributes you
-  # want to serialize. Attributes must be strings, not symbols. When called,
-  # serializable hash will use instance methods that match the name of the
-  # attributes hash's keys. In order to override this behavior, take a look at
-  # the private method +read_attribute_for_serialization+.
-  #
-  # Most of the time though, you will want to include the JSON or XML
-  # serializations. Both of these modules automatically include the
-  # <tt>ActiveModel::Serialization</tt> module, so there is no need to
-  # explicitly include it.
+
+  # An +attributes+ hash must be defined and should contain any attributes you
+  # need to be serialized. Attributes must be strings, not symbols.
+  # When called, serializable hash will use instance methods that match the name
+  # of the attributes hash's keys. In order to override this behavior, take a look
+  # at the private method +read_attribute_for_serialization+.
+  #
+  # Most of the time though, either the JSON or XML serializations are needed.
+  # Both of these modules automatically include the <tt>ActiveModel::Serialization</tt> 
+  # module, so there is no need to explicitly include it.
   #
   # A minimal implementation including XML and JSON would be:
   #