Disable OptionsWebUINavigationTest.ShowSearchPageNoQuery

The test is flaky

BUG=303841
TBR=pam@chromium.org

Review URL: https://codereview.chromium.org/25913002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226808 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226808