chore: enable clippy::redundant_clone (#3489)

Created this PR by:

- adding `redundant_clone` to `[workspace.lints.clippy]` in
`cargo-rs/Cargol.toml`
- running `cargo clippy --tests --fix`
- running `just fmt`

Though I had to clean up one instance of the following that resulted:

```rust
let codex = codex;
```

codex-rs/tui/src/diff_render.rs

@@ -737,10 +737,10 @@ mod tests {
 
         let mut changes: HashMap<PathBuf, FileChange> = HashMap::new();
         changes.insert(
-            abs_old.clone(),
+            abs_old,
             FileChange::Update {
                 unified_diff: patch,
-                move_path: Some(abs_new.clone()),
+                move_path: Some(abs_new),
             },
         );