I found.
It because there is no this file ru-RU.plg_app_user_friends.ini in package
On transifiiex this file is also missing.

Hello Romagromov,

In the latest version of EasySocial, we have merged all language files into /language/en-GB/en-GB.com_easysocial.ini to speed up the site. We have performed some benchmarks on Joomla and when there are tons of language files loaded, it's causing huge delays on the rendering of the page.

So I need manually remove files:

en-GB.plg_app_user_friends.ini
en-GB.plg_app_user_groups.ini
en-GB.plg_app_user_followers.ini

right?

Yes, they are no longer needed