Pin the zip crate to 0.6 (#3645)
## Summary
Restore API-compatibility with pre-1.1.0 versions of the `zip` crate,
and pin the dependency to the 0.6 series, due to concerns discussed in
https://github.com/astral-sh/uv/issues/3642.
## Test Plan
```
cargo run -p uv-dev -- fetch-python
cargo test
```
