fix(pdf-extract): adjust box threshold for OCR detection to fix issue about OCR mode lost some line

[myhloli]

Motivation

Tuned the detection box threshold parameter in the OCR model initialization to improve the accuracy of text extraction from images. The threshold was modified from 0.6 to 0.3 to filter out smaller detection boxes, which is expected to enhance the quality of the extracted text by reducing noise and false positives in the OCR process.

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)

If this PR introduces a new feature, it is better to list some use cases here and update the documentation.

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.