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

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

codex-rs/mcp-server/tests/suite/codex_tool.rs

@@ -200,7 +200,6 @@ fn create_expected_elicitation_request(
             codex_cwd: workdir.to_path_buf(),
             codex_call_id: "call1234".to_string(),
             codex_parsed_cmd,
-            codex_risk: None,
         })?),
     })
 }