Remove trailing slash in base_url

[skasberger]

Remove trailing slash if base_url is passed with one

Change

• [ ] Develop tests
• [ ] Write code
• [ ] Update Docs
• [ ] Update Docstrings

Review

• [ ] Docs
• [ ] Type annotation
• [ ] Linting

Follow-Ups

• [ ]

[pdurbin]

As discussed during the 2024-02-14 meeting of the pyDataverse working group, we are closing old milestones in favor of a new project board at https://github.com/orgs/gdcc/projects/1 and removing issues (like this one) from those old milestones. Please feel free to join the working group! You can find us at https://py.gdcc.io and https://dataverse.zulipchat.com/#narrow/stream/377090-python