fix qnn export (#9808)

Summary:

One missing item for the new tokenizer lib

Differential Revision: D72263224

Author: cccclai

examples/qualcomm/oss_scripts/llama/llama.py

@@ -57,7 +57,6 @@
 from executorch.examples.models.llama.source_transformation.quantize import (
     get_quant_embedding_transform,
 )
-from executorch.examples.models.llama.tokenizer.tiktoken import Tokenizer as Tiktoken
 from executorch.examples.qualcomm.oss_scripts.llama.model.static_llama import (
     LlamaModel,
     ModelArgs,
@@ -77,6 +76,7 @@
 from executorch.extension.llm.export.builder import DType
 from pytorch_tokenizers import get_tokenizer
 from pytorch_tokenizers.llama2c import Llama2cTokenizer as SentencePieceTokenizer
+from pytorch_tokenizers import TiktokenTokenizer as Tiktoken
 
 from torch.ao.quantization.observer import MinMaxObserver
 from torch.ao.quantization.quantize_pt2e import convert_pt2e, prepare_pt2e