Switch gpt3 to BaseLM

lm_eval/models/gpt3.py

 import os
 import numpy as np
 import transformers
-from lm_eval.base import LM, TokenizedLM
+from lm_eval.base import LM, BaseLM
 from lm_eval import utils
 from tqdm import tqdm
 import time
@@ -35,7 +35,7 @@ def oa_completion(**kwargs):
             backoff_time *= 1.5
 
 
-class GPT3LM(TokenizedLM):
+class GPT3LM(BaseLM):
     REQ_CHUNK_SIZE = 20
 
     def __init__(self, engine, truncate=False):