doc: update issue

Author: terryyz

README.md

@@ -347,6 +347,8 @@ We share pre-generated code samples from LLMs we have [evaluated](https://huggin
 
 ## 🐞 Known Issues
 
+- [ ] Due to [the Hugging Face tokenizer update](https://github.com/huggingface/transformers/pull/31305), some tokenizer may be broken and will degrade the performance of the evaluation. Please try `--tokenizer_legacy` during the generation.
+
 - [ ] Due to the flakes in the evaluation, the execution results may vary slightly (~0.2%) between runs. We are working on improving the evaluation stability.
 
 - [ ] You may get errors like `ImportError: /usr/local/lib/python3.10/site-packages/matplotlib/_c_internal_utils.cpython-310-x86_64-linux-gnu.so: failed to map segment from shared object` when running the evaluation. This is due to the memory limit of the docker container. You can increase the memory limit of the docker container to solve this issue.