Unreviewed GTK+ gardening. Skip http/tests/appcache/auth.html after r175776.

Appcache manifest is still downloaded in the WebProcess.

* platform/gtk/TestExpectations:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@176121 268f45cc-cd09-0410-ab3c-d52691b4dbfc