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/cooper-hewitt/default.nix

@@ -1,6 +1,6 @@
-{ stdenv, fetchzip }:
+{ lib, fetchzip }:
 
-fetchzip rec {
+fetchzip {
   name = "cooper-hewitt-2014-06-09";
 
   url = https://www.cooperhewitt.org/wp-content/uploads/fonts/CooperHewitt-OTF-public.zip;
@@ -12,7 +12,7 @@ fetchzip rec {
 
   sha256 = "01iwqmjvqkc6fmc2r0486vk06s6f51n9wxzl1pf9z48n0igj4gqd";
 
-  meta = with stdenv.lib; {
+  meta = with lib; {
     homepage = https://www.cooperhewitt.org/open-source-at-cooper-hewitt/cooper-hewitt-the-typeface-by-chester-jenkins/;
     description = "A contemporary sans serif, with characters composed of modified-geometric curves and arches";
     license = licenses.ofl;