[test] Skip test for arm64 gc stress.

BUG=v8:4779
LOG=n
NOTRY=true
TBR=bmeurer@chromium.org, ulan@chromium.org

Review URL: https://codereview.chromium.org/1729263006

Cr-Commit-Position: refs/heads/master@{#34280}

test/mjsunit/mjsunit.status

@@ -391,6 +391,9 @@
 
   # BUG(v8:4754).
   'debug-referenced-by': [PASS, NO_VARIANTS],
+
+  # BUG(v8:4779): Crashes flakily with stress mode on arm64.
+  'array-splice': [PASS, SLOW, ['arch == arm64', FAST_VARIANTS]],
 }],  # 'gc_stress == True'
 
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