Adds a freshness exemption for StalkWalker. Bug: chromium:422917292 Change-Id: Ie36fc10ac94b0f5e9c657f649cc96ed26b04de12 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6968094 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>