graphviz: drop libXaw and libXpm dependencies

The test build intended for debian [1] uses these dependencies as build time dependencies only.
The arch package [2] does not use these dependencies at all.
libXaw was added 11 years ago in 08131bd5d5.

On arch, xterm links in libXaw and is used for vimdot support.
However, the xterm nix package also explicitly links libXaw [3], and vimdot generally works.
The build succeeds, and with vimdot working (through xwayland), this seems fully non-breaking.

This change will drop libXaw from being a mass rebuild.
While libXaw seems somewhat maintained, recent releases [4] are not even signed anymore,
thus probably should not be a core component of nix packages.

[1] https://gitlab.com/graphviz/graphviz/-/blob/2649f2366435525085cc79fb1e95ec23c84eb047/debian/control#L6
[2] https://archlinux.org/packages/extra/x86_64/graphviz/
[3] https://github.com/NixOS/nixpkgs/blob/a84ebe20c6bc2ecbcfb000a50776219f48d134cc/pkgs/by-name/xt/xterm/package.nix#L40
[4] https://gitlab.freedesktop.org/xorg/lib/libxaw/-/tags#

pkgs/tools/graphics/graphviz/default.nix

@@ -58,7 +58,7 @@ stdenv.mkDerivation rec {
     gts
     pango
     bash
-  ] ++ optionals withXorg (with xorg; [ libXrender libXaw libXpm ])
+  ] ++ optionals withXorg (with xorg; [ libXrender ])
   ++ optionals stdenv.hostPlatform.isDarwin [ ApplicationServices Foundation ];
 
   hardeningDisable = [ "fortify" ];