chore: Upgrade pyproject-toml crate (#7335)
## Summary
This PR bumps the pyproject-toml crate to 0.7.0. The only difference is that it now depends on indexmap 2. I reviewed the indexmap 2 changes and they don't seem relevant to us.
I used this opportunity to remove the default features from `serde_with` which removes our indexmap 1 dependency (and some other unused dependencies)
## Test Plan
`cargo test`
