fix: Remove microfrontends unwrap allow (#12890)
## Why
`turborepo-microfrontends` no longer has implementation `.unwrap()`
usage, but it still carried a crate-level unwrap lint exemption.
Removing the exemption lets the workspace lint prevent regressions.
Closes TURBO-5655
## What
Removes the remaining crate-level `clippy::unwrap_used` allowance from
`turborepo-microfrontends`.
## How
- `cargo fmt -p turborepo-microfrontends`
- `cargo test -p turborepo-microfrontends`
- `cargo clippy -p turborepo-microfrontends --all-targets -- -D
warnings`
- Pre-push hook passed with format, check:toml, and Rust checks
