Revert of [CQ] Make gn bot temporarily experimental. (patchset #1 id:1 of https://codereview.chromium.org/1829673002/ )

Reason for revert:
Bot compiles blink only now and works again.

Original issue's description:
> [CQ] Make gn bot temporarily experimental.
>
> TBR=sergiyb@chromium.org, dpranke@chromium.org
> BUG=chromium:481693
> LOG=n
> NOTRY=true
> NOPRESUBMIT=true
>
> Committed: https://crrev.com/b072760b99f45839e6b4ebeffc46c5d4e8c3a6e3
> Cr-Commit-Position: refs/heads/master@{#35026}

TBR=sergiyb@chromium.org,dpranke@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:481693

Review URL: https://codereview.chromium.org/1826783002

Cr-Commit-Position: refs/heads/master@{#35032}