ci(mergify): upgrade configuration to current format

Author: mergify[bot]

.mergify.yml

@@ -1,12 +1,13 @@
 queue_rules:
   - name: default
-    conditions: []  # no extra conditions needed to get merged
+    queue_conditions:
+      - "#approved-reviews-by>=1"
+    merge_conditions: [] # no extra conditions needed to get merged
+
+    merge_method: squash
 
 pull_request_rules:
   - name: Automatic merge on approval
-    conditions:
-      - "#approved-reviews-by>=1"
+    conditions: []
     actions:
       queue:
-        name: default
-        method: squash