Revert "Drain the CQ starting at 11AM PST for emergency lab network maintenance."

This reverts commit 49993008.

Reason for revert: maintenance over, reenabling CQ

Original change's description:
> Drain the CQ starting at 11AM PST for emergency lab network maintenance.
> 
> Maintenance will last about an hour. Drain the CQ for the duration of
> this.
> 
> NOTRY=true
> TBR=jbudorick, tandrii
> 
> Change-Id: Ic5114c910c431ddd92cacfc323d7cd420cc9657a
> Reviewed-on: https://chromium-review.googlesource.com/1255222
> Reviewed-by: Ben Pastene <bpastene@chromium.org>
> Reviewed-by: John Budorick <jbudorick@chromium.org>
> Commit-Queue: Ben Pastene <bpastene@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#595479}

TBR=tandrii@chromium.org,bpastene@chromium.org,jbudorick@chromium.org

Change-Id: Ia66d9c492cca5001bfffbbc40992f49cd5b108aa
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1255582Reviewed-by: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595486}

infra/config/branch/cq.cfg

@@ -10,7 +10,7 @@ max_commit_burst: 2
 # Trooper, if you want to drain CQ such that CQ stops triggering new trybots,
 # uncomment line below. The timestamp cutoff time in UTC s.t. all CLs
 # on which CQ was triggered **after** this time are ignored by CQ.
-draining_start_time: "2018-10-01T18:00:00Z"
+# draining_start_time: "2018-02-28T20:00:00Z"
 
 gerrit {}