Fix ChainOfThoughtWithHint

[Hangzhi]

Why

Resolve #8205. The community reported that ChainOfThoughtWithHint is broken. By manual verification, it's indeed broken with basic usage as below

class BasicQA(dspy.Signature):
    """Answer questions with short factoid answers."""
    question = dspy.InputField()
    answer = dspy.OutputField(desc="often between 1 and 5 words")

#Pass signature to ChainOfThought module
generate_answer = dspy.ChainOfThoughtWithHint(BasicQA)

# Call the predictor on a particular input alongside a hint.
question='What is the color of the sky?'
hint = "It's what you often see during a sunny day."
pred = generate_answer(question=question, hint=hint)

print(f"Question: {question}")
print(f"Predicted Answer: {pred.answer}")

What

1. Fix the module
2. Uncomment the unit test for the ChainOfThoughtWithHint module

Testing

1. Manual Verification with the BasicQA above
2. Unit test

[okhat]

I think we should just remove this in 3.0

[Hangzhi]

@okhat Opened another PR to clean up ChainOfThoughtWithHint #8395