[tests] Disable slow tests for gc-stress (they time out)

Bug: v8:9506
Change-Id: If570b71d95030dd5fbe31d86d307ab0b45827308
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2306796Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68932}

test/mjsunit/mjsunit.status

@@ -287,6 +287,10 @@
   # Too slow for gc stress.
   'asm/embenchen/box2d': [SKIP],
 
+  # Too slow for gc stress, BUG(v8:9506): times out.
+  'wasm/shared-memory-worker-explicit-gc-stress': [SKIP],
+  'wasm/shared-memory-worker-gc-stress': [SKIP],
+
   # BUG(v8:4237)
   'regress/regress-3976': [SKIP],