nixos/gvfs: fix libmtp udev package path
nixos/gvfs: fix libmtp udev package path

As pointed out by @sigprof[1] my bump of libmtp silently broke this, as I
moved the udev files out of the bin output of the pkg.

[1]: https://github.com/NixOS/nixpkgs/pull/144290#discussion_r775266642

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs