Remove TSan suppression syntax errors

In https://chromium-review.googlesource.com/c/chromium/src/+/1539153, I
cleaned up some dead symbols but, in doing so, I left a stray
"race:base::trace_event::" in the file with no trailing newline. That
line and the suppression following it don't actually do anything useful
as a result and apparently TSan bots have been fine, so remove them.

Bug: 257396
Change-Id: Ic995eff58651c011edee0dd0586d9e598f155fe0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1681449
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706083}

build/sanitizers/tsan_suppressions.cc

@@ -47,11 +47,7 @@ char kTSanDefaultSuppressions[] =
     // http://crbug.com/246968
     "race:webrtc::VideoCodingModuleImpl::RegisterPacketRequestCallback\n"
 
-    // http://crbug.com/257396
-    "race:base::trace_event::"
-
     // http://crbug.com/258479
-    "race:SamplingStateScope\n"
     "race:g_trace_state\n"
 
     // http://crbug.com/268924