[Telemetry] Disable famo.us in key_silk_cases page set.

It is timing out on most platforms.

TBR=rtenneti@chromium.org,dominikg@chromium.org
NOTRY=True
BUG=

Review URL: https://codereview.chromium.org/138143007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244891 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244891