nixos: Remove modprobe.d/nixos.conf from initrd.

For example in VM tests, this causes firmware to be included in the
initrd. So until we have a better fix for adding early-stage module
options, I'll remove this.

Fixes a regression introduced by 0aa2c1d and closes #3764.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/modules/system/boot/stage-1.nix

@@ -199,9 +199,6 @@ let
         { object = pkgs.writeText "mdadm.conf" config.boot.initrd.mdadmConf;
           symlink = "/etc/mdadm.conf";
         }
-        { object = config.environment.etc."modprobe.d/nixos.conf".source;
-          symlink = "/etc/modprobe.d/nixos.conf";
-        }
         { object = pkgs.stdenv.mkDerivation {
             name = "initrd-kmod-blacklist-ubuntu";
             builder = pkgs.writeText "builder.sh" ''