ci(mergify): upgrade configuration to current format

.mergify.yml

@@ -1,26 +1,26 @@
 queue_rules:
   - name: default
-    conditions:
+    queue_conditions:
+      - "#approved-reviews-by>1"
+      - label=automerge
+    merge_conditions:
       - base~=cosmos/
+    commit_message_template: >
+      {{ title }} (#{{ number }})
+
+      {{ body }}
+    merge_method: squash
 
 pull_request_rules:
-  - name: automerge with label automerge and branch protection passing
-    conditions:
-      - "#approved-reviews-by>1"
-      - label=automerge
-    actions:
-      queue:
-        name: default
-        method: squash
-        commit_message_template: >
-          {{ title }} (#{{ number }})
-
-          {{ body }}
   - name: backport patches to v0.47.x branch
     conditions:
       - base=cosmos/v0.50.x
       - label=backport/v0.47.x
     actions:
       backport:
         branches:
-          - cosmos/v0.47.x
+          - cosmos/v0.47.x
+  - name: automerge with label automerge and branch protection passing
+    conditions: []
+    actions:
+      queue: