fix: resolve lint issues in human input event streaming implementation

- Remove unused imports from server modules and test files
- Fix undefined variable references in test assertions
- All ruff checks now pass locally

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

tests/server/test_human_input_server.py

@@ -1,7 +1,4 @@
 import pytest
-import asyncio
-import json
-from unittest.mock import patch, MagicMock
 
 try:
     from fastapi.testclient import TestClient