Fix vocab_source in sample.py

sample.py

@@ -52,7 +52,7 @@ if compile:
     model = torch.compile(model) # requires PyTorch 2.0 (optional)
 
 # load the tokenizer
-vocab_source = checkpoint_dict.get("vocab_source", "llama2")
+vocab_source = checkpoint_dict["config"].get("vocab_source", "llama2")
 vocab_size = gptconf.vocab_size
 if tokenizer:
     # a specific tokenizer is provided, use it