mergify: auto-merge relbot PRs that target the main branch

.mergify.yml

@@ -5,11 +5,16 @@ queue_rules:
         - status-success=complete-pr
         - and:
           # For more context, see "Auto Merge" rules down below
-          - base~=^releases[_/].*
           - status-success=complete-push
           - or:
-            - head~=^automation/sync-strings-\d+
-            - head~=^relbot/fenix-\d+
+            - and:
+              - base~=^releases[_/].*
+              - or:
+                - head~=^automation/sync-strings-\d+
+                - head~=^relbot/fenix-\d+
+            - and:
+              - base=main
+              - head~=^relbot/AC-Nightly-.+
 pull_request_rules:
   - name: Resolve conflict
     conditions: