Turn directions in PR template into comments

[davidmrdavid]

<-- Start the PR description with some context for the change. -->
Currently, the directions in the PR template aren't proper markdown comments, so they need to either be removed from every PR, or manually turned into comments so they won't render.

As an example, see above 👀^

This PR simply turns those directions into comments so that the instructions can be preserved while editing the text without the need to modify them further.

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation PR is ready to merge and referenced in pending_docs.md
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

[ConnorMcMahon]

Thanks for the fixup here!