Remove stale PostTaskToInProcessRendererAndWait TSan suppression

This appears to be fixed now. See
https://bugs.chromium.org/p/chromium/issues/detail?id=454655#c12

Bug: 454655
Change-Id: Ib77a0621aa1857b37e0b356a34ba44b3b9ed7deb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617863
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661807}

build/sanitizers/tsan_suppressions.cc

@@ -174,9 +174,6 @@ char kTSanDefaultSuppressions[] =
     // https://crbug.com/459429
     "race:randomnessPid\n"
 
-    // https://crbug.com/454655
-    "race:content::BrowserTestBase::PostTaskToInProcessRendererAndWait\n"
-
     // http://crbug.com/582274
     "race:usrsctp_close\n"