ci(mergify): upgrade configuration to current format

Author: mergify[bot]

.github/mergify.yml

@@ -15,7 +15,7 @@ pull_request_rules:
     actions:
       queue:
 queue_rules:
-  - queue_branch_merge_method: fast-forward
-    allow_queue_branch_edit: true
+  - allow_queue_branch_edit: true
     update_method: merge
     name: default
+    merge_method: fast-forward