chore: update generate pdf scripts

[YiniXu9506]

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Since the structure of TOC.md has been changed, the parse method for generating PDF is failed. This PR is to fix the parse method.

And this issue caused by #54

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This pull request has been approved by:

• TomShawn

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[TomShawn]

/merge

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This pull request has been accepted and is ready to merge.

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Commit hash: f3c21a0