Remove suppression for race condition in talk_base::Event.

The code that was using Event has been removed, so we shouldn't see this
issue anymore.

BUG=116421

Review URL: https://chromiumcodereview.appspot.com/10261021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@134715 0039d316-1c4b-4281-b951-d872f2087c98

tools/valgrind/tsan/suppressions.txt

@@ -842,11 +842,6 @@
   fun:AudioRendererHost::OnCreated
   fun:media::AudioOutputController::DoCreate
 }
-{
-  bug_116421
-  ThreadSanitizer:Race
-  fun:talk_base::Event::EnsureInitialized
-}
 {
   bug_116559
   ThreadSanitizer:Race