treewide: Add passthru.updateScript to gnome pkgs

`updateScript` lets us update packages automatically.
For packages that are hosted on the gnome mirror it's very easy to add
that. Inspired by https://github.com/NixOS/nixpkgs/issues/36150

pkgs/data/documentation/gnome-user-docs/default.nix

@@ -1,12 +1,20 @@
-{ stdenv, fetchurl, itstool, libxml2, gettext }:
+{ stdenv, fetchurl, itstool, libxml2, gettext, gnome3 }:
 
-stdenv.mkDerivation {
-  name = "gnome-user-docs-3.2.2";
+stdenv.mkDerivation rec {
+  pname = "gnome-user-docs";
+  version = "3.2.2";
 
   src = fetchurl {
-    url = mirror://gnome/sources/gnome-user-docs/3.2/gnome-user-docs-3.2.2.tar.xz;
+    url = "mirror://gnome/sources/${pname}/${stdenv.lib.versions.majorMinor version}/${pname}-${version}.tar.xz";
     sha256 = "1ka0nw2kc85p10y8x31v0wv06a88k7qrgafp4ys04y9fzz0rkcjj";
   };
 
   nativeBuildInputs = [ itstool libxml2 gettext ];
+
+  passthru = {
+    updateScript = gnome3.updateScript {
+      packageName = pname;
+      attrPath = "gnome3.gnome-user-docs";
+    };
+  };
 }

pkgs/data/fonts/ttf-bitstream-vera/default.nix

@@ -1,9 +1,12 @@
-{stdenv, fetchzip}:
+{ stdenv, fetchzip }:
+let
+  pname = "ttf-bitstream-vera";
+  version = "1.10";
+in
+fetchzip rec {
+  name = "${pname}-${version}";
 
-fetchzip {
-  name = "ttf-bitstream-vera-1.10";
-
-  url = mirror://gnome/sources/ttf-bitstream-vera/1.10/ttf-bitstream-vera-1.10.tar.bz2;
+  url = "mirror://gnome/sources/${pname}/${stdenv.lib.versions.majorMinor version}/${name}.tar.bz2";
 
   postFetch = ''
     tar -xjf $downloadedFile --strip-components=1