Bedevere check for issue number is faulty

[vsajip]

In a couple of ways:

• The check seems to be done even when the skip-issue label is present.
• In GH-101164, skip-issue is set. When backports to 3.10 and 3.11 were created, Bedevere wrongly takes the presence of GH-101164 in the revised PR title to suggest that " Issue number 101164 found", which is not the case - GH-101164 is merely the source PR, and not an actual issue.