ci(mergify): upgrade configuration to current format

.github/mergify.yml

@@ -12,8 +12,7 @@ pull_request_rules:
               - milestone~=v[0-9]\.[0-9]{2}
     actions:
       comment:
-        message: This pull request has merge conflicts. Could you please resolve them
-          @{{author}}? 🙏
+        message: This pull request has merge conflicts. Could you please resolve them @{{author}}? 🙏
       label:
         add:
           - waiting-on-author