fix link

tsa/howto/gitlab.mdwn

@@ -301,7 +301,7 @@ that is not covered by the `gitlab-backup` command.
 
 Another cron job purges backups older than two days, in
 `/etc/cron.d/gitlab-rotate-backup`, so that we don't keep too many
-copies on the server. It is assumed that the existing [[backups]]
+copies on the server. It is assumed that the existing [[backup]]
 system will pick up those copies and store them for our normal
 rotation periods.