wlroots: remove broken tag

See: https://github.com/NixOS/nixpkgs/issues/38344#issuecomment-432032834

pkgs/development/libraries/wlroots/default.nix

@@ -85,8 +85,5 @@ in stdenv.mkDerivation rec {
     license     = licenses.mit;
     platforms   = platforms.linux;
     maintainers = with maintainers; [ primeos ];
-    # Marked as broken until the first official/stable release (upstream
-    # request). See #38344 for the public discussion.
-    broken = true;
   };
 }