Fix leaked reference in _as_blocks()

[KetanHegde]

Summary

Fixes #5067.

JM_EscapeStrFromBuffer() and PyUnicode_FromFormat() return new references. In _as_blocks(), text was wrapped with Py_BuildValue("O", text) before being passed to PyTuple_SET_ITEM(). The "O" format increments the reference count, while PyTuple_SET_ITEM() steals the reference it receives, leaving the original reference to text unreleased.

This change passes text directly to PyTuple_SET_ITEM(), transferring ownership to the tuple and avoiding the leaked reference.

Testing

• Built PyMuPDF successfully after the change.
• Ran the existing test suite successfully.

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[KetanHegde]

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[KetanHegde]

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