data/fonts: cleanup

* make font derivations fixed-output where applicable
 * fix dead links
 * `stdenv.lib` -> `lib` where `stdenv` is not involved
 * remove `meta.platforms = [ unix ]` and `meta.platforms = [ linux ]` because the restriction has no sense for data packages

pkgs/data/fonts/sudo/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchzip }:
+{ lib, fetchzip }:
 
 let
   version = "0.37";
@@ -11,7 +11,7 @@ in fetchzip rec {
     mkdir -p $out/share/fonts/truetype/
     unzip -j $downloadedFile \*.ttf -d $out/share/fonts/truetype/
   '';
-  meta = with stdenv.lib; {
+  meta = with lib; {
     description = "Font for programmers and command line users";
     homepage = https://www.kutilek.de/sudo-font/;
     license = licenses.ofl;