nix: update nixpkgs, remove zig.hook, and remove x11-gnome (#10286)

As of NixOS/nixpkgs#473413, `zig.hook` no longer supports
`zig_default_flags`, and now they can and must be provided in
`zigBuildFlags` instead.

Updating also requires removing gnome-xorg since it has been removed
from nixpkgs.

`nix flake check` succeeds on my system (x86_64-linux), with a couple
deprecation warnings that I believe aren't important.

src/extra/bash.zig

@@ -287,7 +287,7 @@ fn writeBashCompletions(writer: *std.Io.Writer) !void {
         \\  else                    prev="${COMP_WORDS[COMP_CWORD-1]}"
         \\  fi
         \\
-        \\  # current completion is double quoted add a space so the curor progresses
+        \\  # current completion is double quoted add a space so the cursor progresses
         \\  if [[ "$2" == \"*\" ]]; then
         \\    COMPREPLY=( "$cur " );
         \\    return;