Set flux to push to master (canada-ca#2238)

Author: sleepycat

deploy/gke/update-automation.yaml

@@ -21,4 +21,4 @@ spec:
         email: fluxcd@users.noreply.github.com
       messageTemplate: '[ci skip] {{range .Updated.Images}}{{println .}}{{end}}'
     push:
-      branch: auto
+      branch: master