nixos/lock-kernel-modules: fix typo in unitConfig

I managed to miss this one somehow ... meh

nixos/modules/security/lock-kernel-modules.nix

···
 
       script = "echo -n 1 > /proc/sys/kernel/modules_disabled";
 
-      unitConfig.ConditionPathIsWritable = "/proc/sys/kernel";
+      unitConfig.ConditionPathIsReadWrite = "/proc/sys/kernel";
 
       serviceConfig = {
         Type = "oneshot";