Merge branch 'hly-enforce-markdown-upload-urls' into 'master'

Enforce new Markdown upload URL format

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/156939



Merged-by: Heinrich Lee Yu <heinrich@gitlab.com>
Approved-by: Dominic Bauer <dbauer@gitlab.com>
Approved-by: Hunar Khanna <hkhanna@gitlab.com>
Approved-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Approved-by: Pavel Shutsin <pshutsin@gitlab.com>
Reviewed-by: Vasilii Iakliushin <viakliushin@gitlab.com>