graphics/mupdf: update to 1.23.9

ChangeLog: https://mupdf.com/releases/history.html

MuPDF 1.23.9 (2024-01-11)

• Fix text moving after redaction.
• Add use-cid-for-unknown-unicode option to stext device.

MuPDF 1.23.8 (2024-01-08)

• Move previously private APIs into public headers so they can be used in python bindings.
• Add version numbers to shared library installation targets on Linux/OpenBSD.
• Avoid setuptools problems for python bindings in python 3.12.
• Fix makefile so python bindings build with tesseract. *

MuPDF 1.23.7 (2023-11-30)

• Fix rendering issue concerning group alpha.
• Fix unexpected HTML table rectangles on subsequent pages.
• Fix text extraction of control characters from PDF.
• Fix bug concerning Stories having page-break-after set.
• Ignore broken structure trees instead of reporting an error.
• Various fixes for pymupdf.

PR: 276132
Reported by: uzsolt@uzsolt.hu (maintainer)