Merge pull request #244188 from mweinelt/engelsystem-php81

nixos/engelsystem: pin php at 8.1

nixos/modules/services/web-apps/engelsystem.nix

···
       '';
 
     services.phpfpm.pools.engelsystem = {
+      phpPackage = pkgs.php81;
       user = "engelsystem";
       settings = {
         "listen.owner" = config.services.nginx.user;