/usr/share/doc/ruby-rails-assets-markdown-it-sup/changelog.Debian.gz is in ruby-rails-assets-markdown-it-sup 1.0.0-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/ruby-rails-assets-markdown-it-sup/../libjs-markdown-it-sup/changelog.Debian.gz