Should let the user know about potential issues with map_rerank chain type in 03L

[dbbnicole]

In LLM 03L - Building LLM Chains Lab notebook - Question 3, when the user tries map_rerank chain type, the model we use ('google/flan-t5-large') may not be powerful enough to consistently generate scores that can be parsed by the default parser in the default prompt in order for the results to be ranked.

The student may see error messages like

Could not parse output: [score between 0 and 100]

There are similar reports of this issue on langchain langchain-ai/langchain#3970

[brookewenig]

Thanks for reporting - fixed in the upcoming release!