Revert of Remove android_rel from CQ since all of its machines are offline. (patchset #1 id:1 of https://codereview.webrtc.org/1459083002/ )

Reason for revert:
Two of the machines are back. They were offline due to extended maintenance work needed.

Original issue's description:
> Remove android_rel from CQ since all of its machines are offline.
>
> BUG=558213
> TBR=phoglund@webrtc.org
>
> Committed: https://crrev.com/392d0c2701ef0112035e496cafcd2e7f0453547f
> Cr-Commit-Position: refs/heads/master@{#10704}

TBR=phoglund@webrtc.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=558213

Review URL: https://codereview.webrtc.org/1454883004

Cr-Commit-Position: refs/heads/master@{#10705}
diff --git a/infra/config/cq.cfg b/infra/config/cq.cfg
index fb07c88..80f6f60 100644
--- a/infra/config/cq.cfg
+++ b/infra/config/cq.cfg
@@ -27,8 +27,7 @@
     buckets {
       name: "tryserver.webrtc"
       builders { name: "android_dbg" }
-      # Remove until crbug.com/558213 is fixed.
-      #builders { name: "android_rel" }
+      builders { name: "android_rel" }
       builders { name: "android_arm64_rel" }
       builders { name: "android_clang_dbg" }
       builders { name: "android_gn_dbg" }