docs(github): fix Closes syntax in PR template

Use 'Closes #[issue]' format (two lines) instead of '- Closes: #'
to properly trigger GitHub's auto-close on merge.

Author: Soushi888

.github/pull_request_template.md

@@ -23,6 +23,8 @@
 
 ## Related
 
-- Closes: #
+Closes #[issue]
+Closes #[issue]
+
 - Depends on: #
 - Follow-up: #