pre-commit: Relax the "issue" search pattern a bit

This way one can specify the "issue" attribuite on another line than the
"software-distribution" tag.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
pre-commit: Only bump the issue date if it has not been changed manually

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>