Merge #17146: github: Add warning for bug reports

5f40d2770a github: Add warning for bug reports (Wladimir J. van der Laan)

Pull request description:

  I've noticed the "Bug" label being added redundantly fairly frequently. I think this might be due to github's templates.

  All in all, the link in https://github.com/bitcoin/bitcoin/issues/new/choose to open a regular issue is a bit hidden from sight. Direct people's attention to it.

ACKs for top commit:
  practicalswift:
    ACK 5f40d2770a - currently it is very easy to miss the tiny "Open a regular issue" link :)
  jonasschnelli:
    ACK 5f40d2770a
  hebasto:
    ACK 5f40d2770a

Tree-SHA512: e6c94c02f9f7d00621b580d406d03f8754173150bf456409ccc474b76fb93ff857ff4a0c652bf5c03d4f1b97ecf29ae0ff7bf8b763207f9c8522b8dcecc20109

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,6 +1,6 @@
 ---
 name: Bug report
-about: Create a report to help us improve
+about: Create a report to help us improve (use this for suspected bugs only, if not sure, open a regular issue below)
 title: ''
 labels: Bug
 assignees: ''