Use different strings on exports page

[brawaru]

Currently the page re-uses strings from other contexts which doesn't fit very well - strings incorrectly lowercase-d and pluralized, when they don't need to be, because it's a table.

This PR changes page to re-use accounts.toots.other directly, and admin.accounts for "Following" and "Follows". This should look more aesthetically pleasing.

I cannot set up local testing Mastodon instance, so please carefully review the changes or test them on your local instance. Thanks!

[Gargron]

Why replace a string that seems to exist specifically for this page, though?

[brawaru]

It's kind of looks off with that “You” prefix being alongside with the ones above and below. And for prefix in general, I think it's redundant because the page itself is suggesting that it's your data to export, probably can remove it from the ones below too.

[brawaru]

Hm, why did CI fail with complaint about unused key? I mean, yeah, there is such change. But I perfectly can see from search that this string is still being used in other files, so it's strange why it fails as unused. Probably cannot use direct access then and must duplicate the string, because I'm not sure there is a magic number that will fall to other plural category in every single language.

[brawaru]

Okay, I have found accounts.posts_tab_heading, which is used on user profiles before “Toots and Replies” tab. I'm not sure this is a good idea to use strings from such different contexts, but this is the only option to avoid string duplication, plus from search it looks safe to re-use. I'll give it a try in a minute.