fix bug of gsm8k_postprocess

[hailsham]

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Motivation

We find the current version of gsm8k_postprocess may be not good enough to find more matched answers. So we update a new version: gsm8k_postprocess_v2.
The following gsm8k-GPT-4-turbo.json was predicted by gpt-4-turbo, we show the the accuracy of these two post-processing methods on the same file gsm8k-GPT-4-turbo.json.

accuracy of gsm8k_postprocess: 15.16
accuracy of gsm8k_postprocess_v2: 80.21

Modification

Please briefly describe what modification is made in this PR.

BC-breaking (Optional)

Does the modification introduce changes that break the backward compatibility of the downstream repositories?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

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Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

After PR:

• If the modification has potential influence on downstream or other related projects, this PR should be tested with those projects.
• CLA has been signed and all committers have signed the CLA in this PR.