Move section titles into comment

Author: weihanglo

.github/PULL_REQUEST_TEMPLATE.md

@@ -14,28 +14,23 @@ Thanks for submitting a pull request 🎉! Here are some tips for you:
 * If your PR is not finished, set it as "draft" PR or add "WIP" in its title.
 * It's ok to use the CI resources to test your PR, but please don't abuse them.
 
-Please DELETE all these comments before submitting the PR.
--->
-
 ### What this PR tries to resolve?
-<!--
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 Explain the motivation behind this change.
 A clear overview along with an in-depth explanation are helpful.
 
 You can use `Fixes #<issue number>` to associate this PR to an existing issue.
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 ### How to test and review this PR?
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 https://doc.crates.io/contrib/tests
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 ### Additional information
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