chore: update shared files

Automated update of shared files from the social-core repository, see
https://github.com/python-social-auth/.github/blob/main/repo-sync.py

Author: nijel

README.md

@@ -28,7 +28,7 @@ Contributions are welcome!
 
 Only the core and Django modules are currently in development. All others are in maintenance only mode, and maintainers are especially welcome there.
 
-See the [https://github.com/python-social-auth/.github/blob/main/CONTRIBUTING.md](CONTRIBUTING.md) document for details.
+See the [CONTRIBUTING.md](https://github.com/python-social-auth/.github/blob/main/CONTRIBUTING.md) document for details.
 
 ## Versioning