Bug#1039606: Don't display unimportant issues as "vulnerable"

[Moritz Muehlenhoff <jmm@debian.org>]

Package: security-tracker
Severity: wishlist

"unimportant" issues don't have security impact, but currently they get shown
as "vulnerable" in red, both in a package overview page, e.g.
https://security-tracker.debian.org/tracker/source-package/c-ares and CVE-specific pages, e.g.
https://security-tracker.debian.org/tracker/CVE-2023-31147

This is a little misleading, since those packages are not actually vulnerable.
It would be nice if such "unimportant" issues it would instead display
"unfixed (no/negligible security impact)" instead. And instead of red maybe
in grey.

Cheers,
        Moritz