ci(mergify): upgrade configuration to current format (#795)

Co-authored-by: Mergify <37929162+mergify[bot]@users.noreply.github.com>

.github/mergify.yml

@@ -1,33 +1,28 @@
+
 pull_request_rules:
   # rebase+merge strategy
-  - actions:
+  - name: Put pull requests in the rebase+merge queue + Put pull requests in the squash+merge
+      queue
+    conditions: []
+    actions:
       queue:
-        name: default
-        # Merge into master with a merge commit
-        method: merge
-        # Update the pr branch with rebase, so the history is clean
-        update_method: rebase
-    name: Put pull requests in the rebase+merge queue
-    conditions:
+queue_rules:
+  - name: duplicated default from Put pull requests in the squash+merge queue
+    queue_conditions:
       - label=merge me
       - 'check-success=Frontend_tests'
       - 'check-success~=.*Backend_tests.*'
-      # - '#approved-reviews-by>=1'
-  # merge+squash strategy
-  - actions:
-      queue:
-        name: default
-        method: squash
-        # both update methods get absorbed by the squash, so we use the most
-        # reliable
-        update_method: merge
-    name: Put pull requests in the squash+merge queue
-    conditions:
       - label=squash+merge me
       - 'check-success=Frontend_tests'
       - 'check-success=Backend_tests'
-      # - '#approved-reviews-by>=1'
-
-queue_rules:
+    merge_conditions: []
+    update_method: merge
+    merge_method: squash
   - name: default
-    conditions: []
+    queue_conditions:
+      - label=merge me
+      - 'check-success=Frontend_tests'
+      - 'check-success~=.*Backend_tests.*'
+    merge_conditions: []
+    update_method: rebase
+    merge_method: merge