Promote win7-rel out of experimental CQ status.

The immediate outage has passed. It's still got pretty high swarming test
pending times, but that was the case prior to the outage, and I don't
think that should block us from adding it back to the CQ.

R=jbudorick, dpranke

Bug: 960100
Change-Id: I6254ddb07da89ed8b85fa410bffbe9d5a332887b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1599876
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657381}
2 files changed