Fix suppression for VideoBearSilent media tests.

TBR=oshima@chromium.org
BUG=487501

Review URL: https://codereview.chromium.org/1139063003

Cr-Commit-Position: refs/heads/master@{#329778}

tools/valgrind/gtest_exclude/content_browsertests.gtest-drmemory_win32.txt

@@ -57,4 +57,4 @@ WebRtcBrowserTest.CanMakeAudioCallAndThenRenegotiateToVideo
 *_ClearKey/EncryptedMediaTest.Playback_*
 
 # https://crbug.com/487501
-*_MediaTest.VideoBearSilentWebm_0
+*/MediaTest.VideoBearSilentWebm/0