[test] Skip flaky test

NOTRY=true

Bug: v8:8964
Change-Id: I63e2ab53f3466a86b498c56fac1b296f1bd4d904
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1530818
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60343}

test/mjsunit/mjsunit.status

@@ -963,6 +963,9 @@
     # skip assertion tests since the stack trace is broken if mjsunit is
     # included in the snapshot
     'mjsunit-assertion-error' : [SKIP],
+
+    # https://crbug.com/v8/8964
+    'compiler/math-floor-global': [PASS, ['gc_stress', SKIP]]
 }], # no_harness
 
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