Follow up to MR41: hide identity-permission-box in urlbar

This MR is more work on #66 (closed), which with this should be truly solved (for now ;-) ).

It hides a menu that (among maybe other things) has the purpose to allow autoplay - it pops up, e.g., on tagesschau.de - see for a visual (it's the wide one between the padlock and reader mode).

I think we can safely hide this without negatively impacting users.