🩹 📝 removes the `hmtl_baseurl` setting from RtD config

[burgholzer]

Description

Sphinx recommends not setting hmtl_baseurl so that RtD can figure it out on its own.

Checklist:

• [x] The pull request only contains commits that are related to it.
• [x] I have added appropriate tests and documentation.
• [x] I have made sure that all CI jobs on GitHub pass.
• [x] The pull request introduces no new warnings and follows the project's style guidelines.