nightly-2023-12-17: chore!: Remove backend field from artifacts (#3819)

# Description

In `kw/remove-partial-backend-code` we removed the opcodes supported
feature, which means that artifacts are no longer compiled based on a
backends feature set.


Closes #1388 

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*



## Additional Context



## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[Exceptional Case]** Documentation to be submitted in a separate
PR.

# PR Checklist\*

- [ ] I have tested the changes locally.
- [ ] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

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Co-authored-by: Tom French <[email protected]>