Update release notes (check SVN commit-after-approval access)

Summary:
I was just granted commit-after-approval access to SVN,
and @clattner recommended I try a test commit.

So, this tweaks the release notes as a test.

Reviewers: hokein, alexfh

Reviewed By: hokein

Subscribers: Wizard

Differential Revision: https://reviews.llvm.org/D39559

llvm-svn: 317261

clang-tools-extra/docs/ReleaseNotes.rst

@@ -63,7 +63,8 @@ Improvements to clang-tidy
   <http://clang.llvm.org/extra/clang-tidy/checks/objc-forbidden-subclassing.html>`_ check
 
   Ensures Objective-C classes do not subclass any classes which are
-  not intended to be subclassed.
+  not intended to be subclassed. Includes a list of classes from Foundation
+  and UIKit which are documented as not supporting subclassing.
 
 - Renamed checks to use correct term "implicit conversion" instead of "implicit
   cast" and modified messages and option names accordingly: