Use test-run-failed-in-postsubmit for bug reporting

This allows reporting bugs only for flaky tests that happened after
a CL lands to rule out WIP test failures.

Bug: none
Change-Id: Id413ecd7f178bf82d66e4c57187c6b8b126fb9f6
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/8263841
Reviewed-by: Sergei Rudenkov <sergeirudenkov@chromium.org>
Commit-Queue: Sergei Rudenkov <sergeirudenkov@chromium.org>
Auto-Submit: Alex Rudenko <alexrudenko@chromium.org>