Remediate use of "blacklist" in push rule check error

What does this MR do?

Remediates use of the term 'blacklist' in the following error:

remote: GitLab: File name changelogs/unreleased/security-disable-exiftool-aiff-djvu.yml was blacklisted by the pattern ^changelogs\/unreleased\/.+$.

Our docs refer to 'prohibited file names' so I've proposed using the verb prohibit rather than verbifying denylist.

File name #{changed_path.path} was prohibited by the denylist pattern #{denylisted_regex}.

related to epic: &3478 Replace use of whitelist with allowlist and blacklist with denylist

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