Fixed wrong link in github

Wrong name of main branch

Author: kolyaka32

README-ru.md

@@ -1,5 +1,5 @@
 # Игра "Крестики-нолики" на c++, SDL3
-[![en](https://img.shields.io/badge/lang-en-green.svg)](https://github.com/kolyaka32/tic-tak-toe-on-SDL-net/blob/main/README.md)  [![ru](https://img.shields.io/badge/lang-ru-green.svg)](https://github.com/kolyaka32/tic-tak-toe-on-SDL-net/blob/main/README-ru.md)
+[![en](https://img.shields.io/badge/lang-en-green.svg)](https://github.com/kolyaka32/tic-tak-toe-on-SDL-net/blob/master/README.md)  [![ru](https://img.shields.io/badge/lang-ru-green.svg)](https://github.com/kolyaka32/tic-tak-toe-on-SDL-net/blob/master/README-ru.md)
 
 Этот репозиторий содержит стандартную игру "крестики-нолики" с локальным и онлайн режимами.