[test] Disable failing weakrefs test on MacOS

NOTRY=true
R=sigurds@chromium.org

Change-Id: I94a735508f2ec4ca0b21e48ee0f486c3189b2d8a
Reviewed-on: https://chromium-review.googlesource.com/c/1293954Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56866}

test/mjsunit/mjsunit.status

@@ -660,6 +660,7 @@
 ['system == macos', {
   # BUG(v8:5333)
   'big-object-literal': [SKIP],
+  'harmony/weakrefs/basics': [SKIP],
 }],  # 'system == macos'
 
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