Disable flaky test

Bug: v8:12638
Change-Id: I88a28b8a17b25ead4a5771870323425772f4f45a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3472873Reviewed-by: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Francis McCabe <fgm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79158}

test/unittests/unittests.status

@@ -79,6 +79,10 @@
   # Tests that need to run sequentially (e.g. due to memory consumption).
   'MachineOperatorReducerTest.Word32EqualWithShiftedMaskedValueAndConstant': [PASS, HEAVY],
   'SequentialUnmapperTest.UnmapOnTeardown': [PASS, HEAVY],
+
+  #https://crbug.com/v8/12638
+  # Test seems super flaky, disabling for now
+  'SandboxTest.PartiallyReservedSandboxPageAllocation':[SKIP],
 }],  # tsan == True
 
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