docs: add new version convenant contribuitor guide link (#32107)

Summary:
## Summary
this PR update available link version in Contributor Covenant.!

cc: yungsters

Changelog:
[General][Changed] Updated to Contributor Covenant v2.1

Pull Request resolved: https://github.com/facebook/react-native/pull/32107

Reviewed By: lunaleaps

Differential Revision: D30616702

Pulled By: yungsters

fbshipit-source-id: b79b07cfa14154fbe948e7bb4d6698925be2cdd4