Revert "Temporary remove android_arm64_dbg_recipe from CQ."

This reverts commit 0a2e609.

Reason for revert: typo && not useful any more.

Original change's description:
> Temporary remove android_arm64_dbg_recipe from CQ.
> 
> TBR=jochen@chromium.org,mgiuca@chromium.org
> 
> Bug: 736215
> Change-Id: I10fe5c623fdedd51ab0039132a07b8a413a06978
> No-Try: True
> Reviewed-on: https://chromium-review.googlesource.com/544885
> Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
> Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#481837}

TBR=mgiuca@chromium.org,tandrii@chromium.org,jochen@chromium.org

Change-Id: Ie58bf3ed01bc35899ec73a63dd1db90ec797becd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 736215
Reviewed-on: https://chromium-review.googlesource.com/544826
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#481840}

infra/config/cq.cfg

@@ -34,8 +34,7 @@ verifiers {
   try_job {
     buckets {
       name: "master.tryserver.chromium.android"
-      // TODO: reenable ASAP; see crbug.com/736215.
-      // builders { name: "android_arm64_dbg_recipe" }
+      builders { name: "android_arm64_dbg_recipe" }
       builders { name: "android_clang_dbg_recipe" }
       builders { name: "android_compile_dbg" }
       builders { name: "android_cronet" }