Add forum badge correct link (#5481)

Author: YanVictorSN

README.md

@@ -4,7 +4,7 @@
 [![Coverage Status](https://codecov.io/gh/OpenZeppelin/openzeppelin-contracts/graph/badge.svg)](https://codecov.io/gh/OpenZeppelin/openzeppelin-contracts)
 [![GitPOAPs](https://public-api.gitpoap.io/v1/repo/OpenZeppelin/openzeppelin-contracts/badge)](https://www.gitpoap.io/gh/OpenZeppelin/openzeppelin-contracts)
 [![Docs](https://img.shields.io/badge/docs-%F0%9F%93%84-yellow)](https://docs.openzeppelin.com/contracts)
-[![Forum](https://img.shields.io/badge/forum-%F0%9F%92%AC-yellow)](https://docs.openzeppelin.com/contracts)
+[![Forum](https://img.shields.io/badge/forum-%F0%9F%92%AC-yellow)](https://forum.openzeppelin.com/)
 
 **A library for secure smart contract development.** Build on a solid foundation of community-vetted code.