[Sheriff] Mark test as flaky.
[Sheriff] Mark test as flaky.

BUG=v8:4279
LOG=n
NOTRY=true
TBR=jarin@chromium.org

Review URL: https://codereview.chromium.org/1233603002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#29560}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh