Bug 1795994 - Migrate decision task over to GCP r=ahal,releng-reviewers,jcristau

Differential Revision: https://phabricator.services.mozilla.com/D159839

.taskcluster.yml

@@ -101,7 +101,7 @@ tasks:
                                 description: 'Created by a [cron task](https://firefox-ci-tc.services.mozilla.com/tasks/${cron.task_id}) (${treeherder_link})'
 
               provisionerId: "${trustDomain}-${repository.level}"
-              workerType: "decision"
+              workerType: "decision-gcp"
 
               tags:
                   $if: 'tasks_for == "hg-push"'