Regenerate _readtags.c with Cython 3.2.4, fixes #25

The pre-generated file was generated by Cython 0.29.35, which emits
calls to private CPython C APIs that were removed in Python 3.13+ (e.g.
_PyLong_AsByteArray, Py_UNICODE, _PyGC_FINALIZED). Regenerating with a
recent Cython fixes compilation on Python 3.13 and later.

Author: sbraz