Fix few typos in the documentation [ci skip]

activemodel/lib/active_model/callbacks.rb

@@ -30,7 +30,7 @@ module ActiveModel
   #   end
   #
   # Then in your class, you can use the +before_create+, +after_create+ and
-  # +around_create+ methods, just as you would in an Active Record module.
+  # +around_create+ methods, just as you would in an Active Record model.
   #
   #   before_create :action_before_create
   #

activesupport/lib/active_support/callbacks.rb

@@ -577,7 +577,7 @@ def __update_callbacks(name) #:nodoc:
       # The callback can be specified as a symbol naming an instance method; as a
       # proc, lambda, or block; as a string to be instance evaluated; or as an
       # object that responds to a certain method determined by the <tt>:scope</tt>
-      # argument to +define_callback+.
+      # argument to +define_callbacks+.
       #
       # If a proc, lambda, or block is given, its body is evaluated in the context
       # of the current object. It can also optionally accept the current object as