rm source prefix, add truncation_side args

convlab2/base_models/t5/create_data.py

convlab2/base_models/t5/goal2dialogue/run_goal2dialogue.sh

convlab2/base_models/t5/nlu/run_multiwoz21_user.sh

convlab2/base_models/t5/nlu/run_multiwoz21_user_context3.sh

convlab2/base_models/t5/nlu/run_tm1_user.sh

convlab2/base_models/t5/nlu/run_tm1_user_context3.sh

convlab2/base_models/t5/nlu/run_tm2_user.sh

convlab2/base_models/t5/nlu/run_tm2_user_context3.sh

convlab2/base_models/t5/nlu/run_tm3_user.sh

convlab2/base_models/t5/nlu/run_tm3_user_context3.sh

convlab2/base_models/t5/rg/run_rg.sh

convlab2/base_models/t5/run_seq2seq.py