http/tests/notifications/legacy/window-show-on-click.html is flakey
https://bugs.webkit.org/show_bug.cgi?id=112499

* platform/mac/TestExpectations:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146004 268f45cc-cd09-0410-ab3c-d52691b4dbfc