Remove the TUI test dependency on codex-cli (#38746)

## What changed

Remove the unused `codex-cli` dev-dependency and the no-op import that kept it
visible to `cargo-shear`. TUI tests continue to locate spawned binaries through
`codex-utils-cargo-bin`.

GitOrigin-RevId: ba5855590c6f0300845170f15f39d77c0611a60a

codex-rs/tui/tests/all.rs

@@ -4,7 +4,4 @@
 // The submodules live in `tests/suite/`.
 mod test_backend;
 
-#[allow(unused_imports)]
-use codex_cli as _; // Keep dev-dep for cargo-shear; tests spawn the codex binary.
-
 mod suite;