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