chore: set up backport rule for 53 (#23871)

Author: aljo242

.mergify.yml

@@ -12,14 +12,14 @@ queue_rules:
     merge_method: squash
 
 pull_request_rules:
-  - name: backport patches to v0.52.x branch
+  - name: backport patches to v0.53.x branch
     conditions:
       - base=main
-      - label=backport/v0.52.x
+      - label=backport/v0.53.x
     actions:
       backport:
         branches:
-          - release/v0.52.x
+          - release/v0.53.x
   - name: backport patches to v0.50.x branch
     conditions:
       - base=main