Update suppression for ffmpeg threading issues.

tools/valgrind/tsan/suppressions.txt

 # There are a few kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 541 matching lines @@
   bug_93932_f
   ThreadSanitizer:Race
   fun:update_context_from_thread
   fun:ff_thread_flush
   ...
   fun:media::FFmpegVideoDecoder::Flush
 }
 {
   bug_93932_g
   ThreadSanitizer:Race
+  ...
   fun:frame_thread_free
   ...
   fun:avcodec_close
   ...
-  fun:media::FFmpegVideoDecoder::ReleaseFFmpegResources
 }
 {
   bug_100020
   ThreadSanitizer:Race
   fun:linked_ptr_internal::join
   fun:linked_ptr::copy
   ...
   fun:HostContentSettingsMap::GetDefaultContentSetting
 }
 {
@@ skipping 272 matching lines @@
   fun:content::BrowserThreadImpl::PostTaskHelper
   fun:content::BrowserThread::PostTask
   fun:AudioRendererHost::OnCreated
   fun:media::AudioOutputController::DoCreate
 }
 {
   bug_116421
   ThreadSanitizer:Race
   fun:talk_base::Event::EnsureInitialized
 }