[ci skip] Use touch; slim wording.

* Rename update -> touch to remain consistent with the other docs
  language of "touch"'ing.
* Remove the sentence that's repeated from just above and rephrase.

activerecord/lib/active_record/counter_cache.rb

@@ -21,8 +21,8 @@ module ClassMethods
       #   # For the Post with id #1, reset the comments_count
       #   Post.reset_counters(1, :comments)
       #
-      #   # For the Post with id #1, reset the comments_count
-      #   # and update the +updated_at+ and/or +updated_on+ attributes.
+      #   # Like above, but also touch the +updated_at+ and/or +updated_on+
+      #   # attributes.
       #   Post.reset_counters(1, :comments, touch: true)
       def reset_counters(id, *counters, touch: nil)
         object = find(id)