ci(mergify): upgrade configuration to current format

mergify[bot] · DavHau · commit 4db8c0694c2d · 2025-05-19T19:25:36.000+07:00
diff --git a/.mergify.yml b/.mergify.yml
@@ -1,16 +1,14 @@
 queue_rules:
   - name: default
+    queue_conditions:
+      - base=main
+      - label~=merge-queue|auto-merge|dependencies
     merge_conditions:
       - check-success=buildbot/nix-build
-defaults:
-  actions:
-    queue:
-      allow_merging_configuration_change: true
-      method: rebase
+    merge_method: rebase
+
 pull_request_rules:
   - name: merge using the merge queue
-    conditions:
-      - base=main
-      - label~=merge-queue|auto-merge|dependencies
+    conditions: []
     actions:
       queue:
