Fix lint issues and add parameter validation

- Remove unused Optional import from mlflow.py
- Add noqa comment for mlflow import in try block
- Add parameter type validation with TypeError for non-boolean inputs
- Add MLflow listener import to events/__init__.py
- Clean up unused imports in test files

Addresses code review feedback from João regarding parameter validation
and return type annotations while fixing CI lint failures.

Co-Authored-By: João <joao@crewai.com>

src/crewai/utilities/events/third_party/mlflow_listener.py

@@ -1,4 +1,4 @@
-from typing import Optional, Dict, Any
+from typing import Dict, Any
 import logging
 
 from crewai.utilities.events.crew_events import (