chore: clippy on redundant closure (#4058)

Add redundant closure clippy rules and let Codex fix it by minimising
FQP

codex-rs/core/tests/suite/exec.rs

@@ -1,6 +1,7 @@
 #![cfg(target_os = "macos")]
 
 use std::collections::HashMap;
+use std::string::ToString;
 
 use codex_core::exec::ExecParams;
 use codex_core::exec::ExecToolCallOutput;
@@ -29,7 +30,7 @@ async fn run_test_cmd(tmp: TempDir, cmd: Vec<&str>) -> Result<ExecToolCallOutput
     assert_eq!(sandbox_type, SandboxType::MacosSeatbelt);
 
     let params = ExecParams {
-        command: cmd.iter().map(|s| s.to_string()).collect(),
+        command: cmd.iter().map(ToString::to_string).collect(),
         cwd: tmp.path().to_path_buf(),
         timeout_ms: Some(1000),
         env: HashMap::new(),