gtk: Disable AddNewSendingServicesTests.

Reliably fails in gtk.

BUG=341326
TBR=petewil@chromium.org

Review URL: https://codereview.chromium.org/147493008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249276 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249276