ci(mergify): upgrade configuration to current format

.mergify.yml

@@ -1,12 +1,24 @@
 queue_rules:
   - name: default
-    conditions:
+    queue_conditions:
       - "#approved-reviews-by>=1"
       - "#changes-requested-reviews-by=0"
       - status-success=test (ubuntu-latest)
       - status-success=test (macos-latest)
       - base=master
       - label=automerge-squash
+    merge_conditions:
+      - "#approved-reviews-by>=1"
+      - "#changes-requested-reviews-by=0"
+      - status-success=test (ubuntu-latest)
+      - status-success=test (macos-latest)
+      - base=master
+      - label=automerge-squash
+    commit_message_template: |
+      {{title}}
+
+      {{body}}
+    merge_method: squash
 
 pull_request_rules:
   - name: Automatic merge (squash)
@@ -18,19 +30,13 @@ pull_request_rules:
       - base=master
       - label=automerge-squash
     actions:
-      queue:
-        method: squash
-        name: default
-        commit_message_template: |
-          {{title}}
-
-          {{body}}
       delete_head_branch: {}
+      queue:
   - name: Clean up automerge tags
     conditions:
       - closed
     actions:
       label:
         remove:
-        - automerge-squash
-        - autoclose
+          - automerge-squash
+          - autoclose