ActiveRecord#to_param docs: fix a few singular/plural errors

activerecord/lib/active_record/base.rb

@@ -2323,15 +2323,15 @@ def id
       # object. The default implementation returns this record's id as a String,
       # or nil if this record's unsaved.
       #
-      # For example, suppose that you have a Users model, and that you have a
-      # <tt>map.resources :users</tt> route. Normally, +users_path+ will
-      # construct an URI with the user object's 'id' in it:
+      # For example, suppose that you have a User model, and that you have a
+      # <tt>map.resources :users</tt> route. Normally, +user_path+ will
+      # construct a path with the user object's 'id' in it:
       #
       #   user = User.find_by_name('Phusion')
       #   user_path(path)  # => "/users/1"
       #
-      # You can override +to_param+ in your model to make +users_path+ construct
-      # an URI using the user's name instead of the user's id:
+      # You can override +to_param+ in your model to make +user_path+ construct
+      # a path using the user's name instead of the user's id:
       #
       #   class User < ActiveRecord::Base
       #     def to_param  # overridden