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

@@ -126,5 +126,3 @@ make smoke-test         # собрать образ и проверить его
 [![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=python-fastapi-rest-api-example)
 
 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=python-fastapi-rest-api-example).
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-See most active contributors on [hexlet-friends](https://friends.hexlet.io/).