Add missing await to wpt/.../service-worker/update.https.html

promise_reject returns a promise and needs await.

Bug: n/a
Change-Id: Ida68b118be05268d9e74c9c22886f9064537e700
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1708663
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Commit-Queue: Makoto Shimazu <shimazu@chromium.org>
Auto-Submit: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679854}
2 files changed