[Docs] Fix references

The Dynaconf refrence was unused, Celery had no URL.

docs/admin/10_install.rst

@@ -252,6 +252,5 @@ Finally, bring the stack up using:
 AlekSIS will be reachable on port 80 if you forgot to configure the environment.
 You are responsible for adding a reverse proxy like nginx providing TLS, etc.
 
-.. _Dynaconf: https://dynaconf.readthedocs.io/en/latest/
 .. _Let's Encrypt: https://certbot.eff.org/instructions
 .. _PyPI: https://pypi.org