[test] Skpping flaky object-seal test on TSAN

NOTRY=true

TBR=machenbach@chromium.org

Bug: v8:8294
Change-Id: Ib235139087bd6a651dc8bd43c5f9990e0513c7a5
Reviewed-on: https://chromium-review.googlesource.com/c/1276627
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56573}

test/mjsunit/mjsunit.status

@@ -467,6 +467,9 @@
   'regress/wasm/regress-694433': [SKIP],
   'es6/typedarray': [PASS, NO_VARIANTS],
   'regress/regress-752764': [PASS, NO_VARIANTS],
+
+  # BUG(v8:8294). Started flaking from seemingly unrelated commits, investigating.
+  'object-seal': [SKIP],
 }],  # 'tsan == True'
 
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