Disable WebrtcVideoQualityBrowserTest.MANUAL_TestVGAVideoQuality on Windows.

Flaky time out.

TBR=fischman@chromium.org

BUG=340609

Review URL: https://codereview.chromium.org/148983005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248698 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248698