Sync dependencies, update cookiecutter

[Zeitsperre]

Pull Request Checklist:

• This PR addresses an already opened issue (for bug fixes / features)
  • This PR fixes #xyz
• (If applicable) Documentation has been added / updated (for bug fixes / features).
• (If applicable) Tests have been added.
• CHANGELOG.rst has been updated (with summary of main changes).
  • Link to issue (:issue:number) and pull request (:pull:number) has been added.

What kind of change does this PR introduce?

• Synchronizes dependencies between conda and pip
• Updates the cookiecutter template
• Adds some lower pins on existing dependencies

Does this PR introduce a breaking change?

It should not.

Other information:

There are a few dependencies that I think we can safely remove (e.g. xdoctest). I'll be adding the deptry hook to the template so that we can perform that analysis everywhere.