Relax another check in wxStopWatch unit test.

Increase the upper bound even further to avoid spurious failures in the
buildbot builds.

tests/events/stopwatch.cpp

@@ -103,7 +103,7 @@ void StopWatchTestCase::Misc()
     WX_ASSERT_MESSAGE
     (
         ("Actual time value is %ld", t),
-        t > sleepTime - tolerance && t < sleepTime + tolerance
+        t > sleepTime - tolerance && t < 2*sleepTime
     );
 
     sw.Pause();