Fix mirrors that have invalid SSH public auth mode set
From https://gitlab.com/gitlab-org/gitlab-ce/issues/55729, there are more than 129 pull mirrors that have an invalid auth set because the user may have had previously configured the mirror with SSH credentials. This post-deploy migration switches any pull mirrors to password mode that fall under the criteria:
- They are using SSH public key auth
- They have an import_url that starts with
http