hide note message for pull request template (#17529)

Co-authored-by: John Olheiser <john.olheiser@gmail.com>

.github/pull_request_template.md

@@ -1,7 +1,9 @@
+<!--
+
 Please check the following:
 
 1. Make sure you are targeting the `main` branch, pull requests on release branches are only allowed for bug fixes.
 2. Read contributing guidelines: https://github.com/go-gitea/gitea/blob/master/CONTRIBUTING.md
 3. Describe what your pull request does and which issue you're targeting (if any)
 
-**You MUST delete the content above including this line before posting, otherwise your pull request will be invalid.**
+-->