Remove base::Thread::StopSoon suppression

The original instance was fixed in
https://codereview.chromium.org/2973723003. Remove the suppression.

Bug: 258935
Change-Id: If8fa62961505d45a83a8917121e8f4262a97213d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1625017
Commit-Queue: Gabriel Charette <gab@chromium.org>
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#662375}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0af49711412bff18824a4db286ffdf1064d2f28e

sanitizers/tsan_suppressions.cc

@@ -97,9 +97,6 @@ char kTSanDefaultSuppressions[] =
     "race:base::PowerMonitor::RemoveObserver\n"
     "race:base::PowerMonitor::IsOnBatteryPower\n"
 
-    // http://crbug.com/258935
-    "race:base::Thread::StopSoon\n"
-
     // http://crbug.com/272095
     "race:base::g_top_manager\n"