ci: update mergify

.mergify.yml

@@ -1,18 +1,15 @@
+queue_rules:
+  - name: Agoric
+    conditions:
+      - base=Agoric
+
 pull_request_rules:
   - name: automerge to main with label automerge and branch protection passing
     conditions:
       - "#approved-reviews-by>0"
-      - base=main
+      - base=Agoric
       - label=automerge
     actions:
-      merge:
+      queue:
+        name: Agoric
         method: squash
-        strict: true
-  - name: backport patches to v4.2.x branch
-    conditions:
-      - base=main
-      - label=backport/4.2.x
-    actions:
-      backport:
-        branches:
-          - release/v4.2.x