ci(mergify): upgrade configuration to current format

Author: mergify[bot]

.mergify.yml

@@ -1,8 +1,14 @@
 queue_rules:
   - name: default
-    conditions:
+    queue_conditions:
+      - and:
+          - label=dependencies
+          - base=master
+          - check-success~=build \(2.13.\d+\)
+    merge_conditions:
       # Conditions to get out of the queue (= merged)
       - check-success~=build \(2.13.\d+\)
+    merge_method: squash
 
 pull_request_rules:
 
@@ -12,14 +18,7 @@ pull_request_rules:
     actions:
       label:
         add: [dependencies, scala]
-
   - name: Merge dependency-update PRs
-    conditions:
-      - and:
-        - label=dependencies
-        - base=master
-        - check-success~=build \(2.13.\d+\)
+    conditions: []
     actions:
       queue:
-        name: default
-        method: squash