[mjsunit] Skip slow test for now

TBR=clemensh@chromium.org

No-Try: true
Bug: v8:9506
Change-Id: Id7d0379f82fc0327063c910a650034fba831802d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1706483Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62780}

test/mjsunit/mjsunit.status

@@ -80,6 +80,9 @@
   # Too slow in debug mode, due to large allocations.
   'regress/regress-crbug-941743': [PASS, ['mode == debug', SKIP], ['(arch == arm or arch == arm64 or arch == mipsel or arch == mips64el) and simulator_run == True', SKIP]],
 
+  # Too slow in debug mode BUG(v8:9506): times out.
+  'wasm/shared-memory-worker-explicit-gc-stress': [PASS, ['mode == debug', SKIP]],
+
   ##############################################################################
   # Only RegExp stuff tested, no need for extensive optimizing compiler tests.
   'regexp-global': [PASS, NO_VARIANTS],