Disable another wxStopWatch test case in the build bot builds.

We can't rely on the program waking up quickly enough when running on the
(loaded) buildbot machines, better to skip this test than to have spurious
failures.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76598 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775