Skip flaky test262 Atomics test

TBR=binji@chromium.org

Bug: v8:7876
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Ic98cb9a8f54980e563b765356adfd2653965ff9a
Reviewed-on: https://chromium-review.googlesource.com/1110135Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53942}

test/test262/test262.status

@@ -649,6 +649,10 @@
   'built-ins/Atomics/wake/count-defaults-to-infinity-undefined': [SKIP],
   'built-ins/Atomics/wake/undefined-index-defaults-to-zero': [SKIP],
 
+  # Flaky failure
+  # https://bugs.chromium.org/p/v8/issues/detail?id=7876
+  'built-ins/Atomics/wait/waiterlist-block-indexedposition-wake': [SKIP],
+
   ##################### DELIBERATE INCOMPATIBILITIES #####################
 
   # https://github.com/tc39/ecma262/pull/889