docs(readme): убрать упоминание закрытого hexlet-friends

Сервис friends.hexlet.io закрыт, адрес редиректит на ru.hexlet.io.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: fey

README.md

@@ -55,5 +55,3 @@ parameters:
 [![Hexlet Ltd. logo](https://raw.githubusercontent.com/Hexlet/assets/master/images/hexlet_logo128.png)](https://hexlet.io/?utm_source=github&utm_medium=link&utm_campaign=phpstan-functional-programming)
 
 This repository is created and maintained by the team and the community of Hexlet, an educational project. [Read more about Hexlet](https://hexlet.io/?utm_source=github&utm_medium=link&utm_campaign=phpstan-functional-programming).
-
-See most active contributors on [hexlet-friends](https://friends.hexlet.io/).