chore: some installed deps are not needed

Some dependencies specified in `Cargo.toml` are not needed.

Check the [unused dependencies sanity check](https://github.com/argumentcomputer/sphinx/actions/runs/12110473596) workflow for details.

> **Note**
> If this is a false positive, please refer to the [`cargo-udeps` docs][cargo-udeps-docs] on how to ignore the dependencies.

[cargo-udeps-docs]: https://github.com/est31/cargo-udeps#ignoring-some-of-the-dependencies

Open Cargo.toml and inspect the linked unused dependencies sanity-check workflow; begin by identifying the reported dependencies and checking the cargo-udeps guidance for false positives. Done means the unnecessary entries are removed or appropriately ignored and the sanity check no longer reports them.

Written by the indexing model from the issue text.