Fix MQTT client mock in test configuration

- Update mock import from 'paho.mqtt.client.Mosquitto' to 'paho.mqtt.client.Client'
- Ensure compatibility with latest Paho MQTT client testing

Author: fbeneventi

tests/conftest.py

@@ -40,7 +40,7 @@ def temp_config_file():
 @pytest.fixture
 def mock_mqtt_client(mocker):
     """Mocks MQTT client for testing"""
-    mock_client = mocker.patch('paho.mqtt.client.Mosquitto')
+    mock_client = mocker.patch('paho.mqtt.client.Client')
     return mock_client
 
 @pytest.fixture