Remove dovecot service name compat code

mail-server/users.nix

@@ -117,7 +117,7 @@ in
 
     systemd.services.activate-virtual-mail-users = {
       wantedBy = [ "multi-user.target" ];
-      before = [ "${dovecotUnitName}.service" ];
+      before = [ "dovecot.service" ];
       serviceConfig = {
         ExecStart = virtualMailUsersActivationScript;
       };