update PR template (#24837)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,8 +1,9 @@
-<!--  Demo: PR types: Bug fixes, Function optimization  -->
+<!-- Demo: https://github.com/PaddlePaddle/Paddle/pull/24810 -->
+### PR types
 <!-- One of [ New features | Bug fixes | Function optimization | Performance optimization | Breaking changes | Others ] -->
-PR types:
-<!--  Demo: PR changes: OPs  -->
+
+### PR changes
 <!-- One of	[ OPs | APIs | Docs | Others ] -->
-PR changes:
+
+### Describe
 <!-- Describe what this PR does -->
-Describe: