fixed imports in audio perturbation unit tests

Signed-off-by: Swanand Ravindra Kadhe <[email protected]>

Author: Swanand-Kadhe

tests/attacks/poison/test_audio_perturbations.py

@@ -20,7 +20,7 @@
 import logging
 import numpy as np
 import pytest
-import os, sys
+import os
 
 from art.attacks.poisoning.perturbations.audio_perturbations import insert_tone_trigger, insert_audio_trigger