update PR template (#24837)

.github/PULL_REQUEST_TEMPLATE.md

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