ci(mergify): upgrade configuration to current format

.mergify.yml

@@ -1,22 +1,21 @@
----
+
 pull_request_rules:
-  - actions:
+  - name: default
+    conditions: []
+    actions:
       queue:
-        method: merge
-        name: default
-    conditions:
+queue_rules:
+  - name: default
+    queue_conditions:
       - label=ready-to-merge
       - '#approved-reviews-by>=1'
       - status-success=lint
       - status-success=docs
       - status-success=test
       - status-success=docs/readthedocs.org:crate-operator
-    name: default
-
-queue_rules:
-  - conditions:
+    merge_conditions:
       - check-success=lint
       - check-success=docs
       - check-success=test
       - check-success=docs/readthedocs.org:crate-operator
-    name: default
+    merge_method: merge