RU: Translation fixes (#8652)

* RU: Fixed typos and wrong translations

* RU: Added missing "chosen_languages" string

* RU: Fixed translation for "Features" tab in Admin Dashboard

* Shortened "Mobile apps" string, lowercased "following" string (it needs plurals btw), fixed typo at "copy" string.

* Fixed "media only" string, shortened "Content warning" placeholder, edited "mute thread" translation

* RU: Fixed "Reply to all" translation, Re-worded "short description" translation