chore: Update mergify config (#2560)

Update mergify config

Author: Eric-Warehime

.mergify.yml

@@ -73,4 +73,12 @@ pull_request_rules:
     actions:
       backport:
         branches:
-          - release/v6.4.x
+          - release/v6.4.x
+  - name: Backport patches to the release/v7.0.x branch
+    conditions:
+      - base=main
+      - label=A:backport/v7.0.x
+    actions:
+      backport:
+        branches:
+          - release/v7.0.x