Fix LGTM alert

Author: Jostar Yang

platform/broadcom/sonic-platform-modules-accton/as5835-54x/utils/accton_as5835_54x_pddf_monitor.py

@@ -28,7 +28,6 @@
     import logging.config
     import time
     import signal
-    from tabulate import tabulate
     from sonic_platform import platform
 except ImportError as e:
     raise ImportError('%s - required module not found' % str(e))