cq.cfg: use presubmit builder to tryserver.infra.

Corresponding build CL: https://codereview.chromium.org/1759553007,
land OR revert both Cls in tandem.

TBR=phajdan.jr@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1763013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299098 0039d316-1c4b-4281-b951-d872f2087c98

infra/config/cq.cfg

@@ -29,9 +29,9 @@ verifiers {
 
   try_job {
     buckets {
-      name: "tryserver.chromium.linux"
+      name: "tryserver.infra"
       builders {
-        name: "depot_tools_presubmit"
+        name: "Depot Tools Presubmit"
       }
     }
   }