remove preferenced based irl entry(used for trex, drex before)

Author: ruoyuGao

ding/entry/__init__.py

@@ -18,12 +18,7 @@
       episode_to_transitions, episode_to_transitions_filter
 from .application_entry_trex_collect_data import trex_collecting_data, collect_episodic_demo_data_for_trex
 from .serial_entry_guided_cost import serial_pipeline_guided_cost
-from .serial_entry_gail import serial_pipeline_gail
 from .utils import random_collect
-from .serial_entry_preference_based_irl \
-      import serial_pipeline_preference_based_irl
-from .serial_entry_preference_based_irl_onpolicy \
-      import serial_pipeline_preference_based_irl_onpolicy
 from .application_entry_drex_collect_data import drex_collecting_data
 from .serial_entry_mbrl import serial_pipeline_dyna, serial_pipeline_dream
 from .serial_entry_bco import serial_pipeline_bco