[test] Skip flaky test

NOTRY=true
TBR=hablich@chromium.org

Bug: v8:7632
Change-Id: I42e6b3f3585c8a98750ac39de06934174f2a2fa4
Reviewed-on: https://chromium-review.googlesource.com/999417Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52456}

test/mozilla/mozilla.status

@@ -1009,6 +1009,11 @@
   'js1_5/extensions/regress-355497': [FAIL_OK, '--sim-stack-size=512'],
 }],  # 'arch == arm64 and simulator_run'
 
+['tsan', {
+  # https://crbug.com/v8/7632
+  'ecma_3/RegExp/regress-85721': [SKIP],
+}],  # tsan
+
 ['variant == wasm_traps', {
   '*': [SKIP],
 }],  # variant == wasm_traps