Second release candidate for PyMuPDF-1.21.0: PyMuPDF-1.21.0rc2

This is largely unchanged from 1.21.0rc1, except that it builds with the official MuPDF-1.21.0 release.

Install with: python -m pip install pymupdf==1.21.0rc2

• Uses mupdf-1.21.0.
• New Story support.
• Added wheels for Python-3.11.
• Docs: https://pymupdf.readthedocs.io/en/1.21.0rc2/
  • Changelog: https://pymupdf.readthedocs.io/en/1.21.0rc2/changes.html