Re-runs PR on title being changed (#4172)

.taskcluster.yml

@@ -128,7 +128,7 @@ tasks:
             source: ${repository}/raw/${head_rev}/.taskcluster.yml
       in:
         $flatten:
-          - $if: 'tasks_for == "github-pull-request" && event["action"] in ["opened", "reopened", "synchronize"]'
+          - $if: 'tasks_for == "github-pull-request" && event["action"] in ["opened", "reopened", "edited", "synchronize"]'
             then:
               $let:
                 pull_request_title: ${event.pull_request.title}