Make logrotate run as git user for source installations
Closes: https://gitlab.com/gitlab-org/gitlab/-/issues/205227
In https://docs.gitlab.com/ee/install/installation.html#set-up-logrotate, we ask users to copy this script. Without su
parameter, it will be vulnerable to CVE-2019-15741. This was already fixed in omnibus-gitlab packages as part of omnibus-gitlab#4380 (closed).