github: Update mergify config to replace deprecated attributes

!! Action Required !!

The configuration uses the deprecated merge_method attribute of the
queue action in one or more pull_request_rules. It must now be used
under the queue_rules configuration.
A brownout is planned on August 26th, 2024.
This option will be removed on September 23rd, 2024.
For more information: https://docs.mergify.com/configuration/file-format/#queue-rules

!! Action Required !!

The configuration uses the deprecated update_method attribute of the
queue action in one or more pull_request_rules. It must now be used
under the queue_rules configuration.
A brownout is planned on August 26th, 2024.
This option will be removed on September 23rd, 2024.
For more information: https://docs.mergify.com/configuration/file-format/#queue-rules

ref: https://docs.mergify.com/workflow/actions/queue/#parameters

Signed-off-by: Anoop C S <anoopcs@cryptolab.net>

.github/mergify.yml

@@ -1,11 +1,4 @@
 ---
-defaults:
-  actions:
-    queue:
-      name: default
-      method: rebase
-      update_method: rebase
-
 # each test should be listed separately, do not use regular expressions:
 # https://docs.mergify.io/conditions.html#validating-all-status-check
 # Until mergify allows us to have default conditions, we will need to
@@ -19,6 +12,8 @@ queue_rules:
       - check-success=test-suite (pacific)
       - check-success=test-suite (quincy)
       - check-success=test-suite (reef)
+    merge_method: rebase
+    update_method: rebase
 
 pull_request_rules:
   # Clearing approvals after content changes