linuxPackages.nvidia_x11: Remove us prefix from mirror

At the time of the last upgrade, the new driver wasn't available on
anything but their US mirror. Pinning to the US mirror isn't
recommended or preferable, but I did it anyway to be able to get the
upgrade out.

(cherry picked from commit 634a098)

pkgs/os-specific/linux/nvidia-x11/default.nix

@@ -29,12 +29,12 @@ stdenv.mkDerivation {
   src =
     if stdenv.system == "i686-linux" then
       fetchurl {
-        url = "http://us.download.nvidia.com/XFree86/Linux-x86/${versionNumber}/NVIDIA-Linux-x86-${versionNumber}.run";
+        url = "http://download.nvidia.com/XFree86/Linux-x86/${versionNumber}/NVIDIA-Linux-x86-${versionNumber}.run";
         sha256 = "1fw87nvbf8dmy7clwmm7jwp842c78mkz9bcb060wbihsywkfkm23";
       }
     else if stdenv.system == "x86_64-linux" then
       fetchurl {
-        url = "http://us.download.nvidia.com/XFree86/Linux-x86_64/${versionNumber}/NVIDIA-Linux-x86_64-${versionNumber}.run";
+        url = "http://download.nvidia.com/XFree86/Linux-x86_64/${versionNumber}/NVIDIA-Linux-x86_64-${versionNumber}.run";
         sha256 = "0lc87bgr29l9idhy2a4bsplkwx9r0dz9kjhcc5xq2xqkkyr5sqd1";
       }
     else throw "nvidia-x11 does not support platform ${stdenv.system}";