cvat-sdk: remove broken and unused body-to-params conversion

[SpecLad]

It's broken, because it generates a multipart/form-data body that Django REST Framework cannot parse. DRF doesn't examine the individual Content-Type headers of parts, so it interprets the JSON-encoded values as str()-encoded values, which corrupts them.

Since this logic is also currently unused (and it's unclear whether it will ever be used again), remove it.

Motivation and context

This is a follow-up to #5058.

How has this been tested?

Relying on CI for this.

Checklist

• [x] 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~~
• [x] 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

• [x] 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.

[nmanovic]

/check

[github-actions[bot]]

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[nmanovic]

@SpecLad , what is the next step with the PR?

[SpecLad]

@SpecLad , what is the next step with the PR?

It's on the backburner for now, because some tests don't pass and I can't fix them easily. It's not blocking anything, so I'll come bsck to it if this issue becomes relevant again (or if I have a spare minute).

[SpecLad]

I decided to fix this in a different way. I'll open a new PR, since it won't have much in common with this.