re-add shared_by_followed_users and in_followed_studios?

The methods `shared_by_followed_users ` and `in_followed_studios` were commented out a while ago 'because it is unclear if there is any case in which the response is not empty'

I could test this because I have an account from ~2017, so should these be reimplemented/checked?

note: when I log into my old account (kay426), these categories do in fact appear on the front page