Avoid deprecated function call for entry setup

[mathebox]

This pull request resolves two deprecation warnings when calling async_forward_entry_setup:

1. Use await Detected code that calls async_forward_entry_setup for integration teufel_raumfeld [..], during setup without awaiting async_forward_entry_setup, which can cause the setup lock to be released before the setup is done. This will stop working in Home Assistant 2025.1.
2. Use async_forward_entry_setups over async_forward_entry_setup Detected that custom integration 'teufel_raumfeld' calls async_forward_entry_setup for integration, teufel_raumfeld […], which is deprecated and will stop working in Home Assistant 2025.6, await async_forward_entry_setups instead

Check this post for further reading: https://developers.home-assistant.io/blog/2024/06/12/async_forward_entry_setups/

Hope you don't mind me not creating separate tickets for this small fix. ✌️