Allow trailing slashes in SDK client url

[zhiltsov-max]

Motivation and context

Closes #5046

• Allowed trailing slashes in Client(url=) and make_client(host=) of CVAT SDK

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (read github docs)
• I have increased versions of npm packages if it is necessary (cvat-canvas,
  cvat-core, cvat-data and cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[SpecLad]

For URLs this makes sense, but I don't think we should be doing this for hosts. Slashes are not valid in host names.

[zhiltsov-max]

Slashes are not valid in host names.

Hm, I don't think the majority of users know about this, and even it they do, it's still very easy to make this mistake.

[SpecLad]

OK, it looks like the host parameter basically already accepts full URLs, so might as well.

[zhiltsov-max]

@nmanovic , this PR is ready for merging.