Revert "[test] Skpping flaky object-seal test on TSAN"

This reverts commit b5800a63.

Reason for revert: Proper fix has already landed, see https://chromium-review.googlesource.com/c/v8/v8/+/1278386

Original change's description:
> [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}

TBR=machenbach@chromium.org,mslekova@chromium.org

Change-Id: I641aa14c2a5c4a4d1db3cde6048cf355b59e4f7c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:8294
Reviewed-on: https://chromium-review.googlesource.com/c/1278795Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56610}

test/mjsunit/mjsunit.status

@@ -467,9 +467,6 @@
   '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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