modules/snipe-it: make phpfpm use phpPackage

We only used phpPackage for artisan script but not for the actual PHPFPM
instance running the service.  This didn't cause any harm as long as the
default PHP instance was php74 but with the switch to php80 this should
be corrected, as Snipe-IT isn't compatible with 8.0.

modules/services/snipe-it.nix

@@ -330,7 +330,7 @@ in {
     };
 
     services.phpfpm.pools.snipe-it = {
-      inherit user group;
+      inherit user group phpPackage;
       phpOptions = ''
         log_errors = on
         post_max_size = ${cfg.maxUploadSize}