[test] Disable mjsunit/regress/regress-crbug-620253 on TSAN

Bug: v8:12920
Change-Id: Iec1f4a2effc45299e30ecf8a586c535dbb22ee20
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3676860
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80815}

test/mjsunit/mjsunit.status

@@ -705,6 +705,9 @@
 
   # BUG(v8:12822): Flakes on TSAN.
   'regress/regress-crbug-1239907': [SKIP],
+
+  # BUG(v8:12920): Breaks on TSAN.
+  'regress/regress-crbug-620253': [SKIP],
 }],  # 'tsan == True'
 
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