onionshare: drop disabled = !isPy3k after Python2 EOL

pkgs/applications/networking/onionshare/default.nix

···
         inherit (tor) geoip;
       })
     ];
-    disabled = !isPy3k;
     propagatedBuildInputs = [
       colorama
       flask
···
       ./fix-qrcode-gui.patch
     ];
 
-    disabled = !isPy3k;
     propagatedBuildInputs = [
       onionshare
       pyqt5