chore: improve bug report template instructions (#11537)

This PR makes it so that in the issue template a line about how to check
boxes is in comment form you can only see it when you are creating the
issue and it does not need to be displayed to everyone.

Author: MrBrain295

.github/ISSUE_TEMPLATE/bug_report.md

@@ -9,7 +9,7 @@ assignees: ''
 
 ### Prerequisites
 
-Please put an X between the brackets as you perform the following steps:
+<!-- Please put an X between the brackets as you perform the following steps: -->
 
 * [ ] Check that your issue is not already filed:
       https://github.com/leanprover/lean4/issues