modules/nvidia-optimus: fix module blacklisting

nixos/modules/services/hardware/nvidia-optimus.nix

···
   ###### implementation
 
   config = lib.mkIf config.hardware.nvidiaOptimus.disable {
-    boot.blacklistedKernelModules = ["nouveau" "nvidia" "nvidiafb"];
+    boot.blacklistedKernelModules = ["nouveau" "nvidia" "nvidiafb" "nvidia-drm"];
     boot.kernelModules = [ "bbswitch" ];
     boot.extraModulePackages = [ kernel.bbswitch ];