Revert of Exclude offline bots from CQ config. (patchset #1 id:1 of https://codereview.webrtc.org/1420283013/ )

Reason for revert:
The a-lab is back online!

Original issue's description:
> Exclude offline bots from CQ config.
>
> To unblock the CQ, let's remove these bots until they're
> back.
>
> BUG=chromium:550814
> TBR=phoglund@webrtc.org
>
> Committed: https://crrev.com/32a6eae610d5e0af055b37b844c517549a31a3eb
> Cr-Commit-Position: refs/heads/master@{#10489}

TBR=phoglund@webrtc.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:550814

Review URL: https://codereview.webrtc.org/1416793007

Cr-Commit-Position: refs/heads/master@{#10496}
diff --git a/infra/config/cq.cfg b/infra/config/cq.cfg
index 0abcf67..80f6f60 100644
--- a/infra/config/cq.cfg
+++ b/infra/config/cq.cfg
@@ -26,9 +26,9 @@
   try_job {
     buckets {
       name: "tryserver.webrtc"
-      #builders { name: "android_dbg" }  # crbug.com/550814
+      builders { name: "android_dbg" }
       builders { name: "android_rel" }
-      #builders { name: "android_arm64_rel" }  # crbug.com/550814
+      builders { name: "android_arm64_rel" }
       builders { name: "android_clang_dbg" }
       builders { name: "android_gn_dbg" }
       builders { name: "android_gn_rel" }