font-awesome: make font-awesome_5 the defautl

It is confusing that font-awesome_4 is the font,
one get when installing font-awesome-ttf.
I don't really see a use case to keep the old version around.

pkgs/data/fonts/font-awesome-4/default.nix

@@ -1,28 +0,0 @@
-{ stdenv, fetchzip }:
-
-let
-  version = "4.7.0";
-in fetchzip rec {
-  name = "font-awesome-${version}";
-
-  url = "https://github.com/FortAwesome/Font-Awesome/archive/v${version}.zip";
-
-  postFetch = ''
-    mkdir -p $out/share/fonts
-    unzip -j $downloadedFile Font-Awesome-${version}/fonts/fontawesome-webfont.ttf -d $out/share/fonts/truetype
-  '';
-
-  sha256 = "0w8y7gxbqiy444phg4jl89kc5hq3jffbkhab8p110qy9jx8s106s";
-
-  meta = with stdenv.lib; {
-    description = "Font Awesome - TTF font";
-    longDescription = ''
-      Font Awesome gives you scalable vector icons that can instantly be customized.
-      This package includes only the TTF font. For full CSS etc. see the project website.
-    '';
-    homepage = http://fortawesome.github.io/Font-Awesome/;
-    license = licenses.ofl;
-    platforms = platforms.all;
-    maintainers = with maintainers; [ abaldeau ];
-  };
-}