Removed experimental "command risk assessment" feature (#7799)

This experimental feature received lukewarm reception during internal
testing. Removing from the code base.

codex-rs/exec/src/lib.rs

@@ -200,7 +200,6 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
         include_apply_patch_tool: None,
         show_raw_agent_reasoning: oss.then_some(true),
         tools_web_search_request: None,
-        experimental_sandbox_command_assessment: None,
         additional_writable_roots: add_dir,
     };