Upgrade Cython for Python 3.13 compatibility

[CyanoKobalamyne]

Currently, compiling the Python bindings with Python 3.13 results in the following error message:

 ../../../python/smt_switch/smt_switch_imp.pxi:536:7: error: use of undeclared identifier '_PyDict_SetItem_KnownHash'
  if (__Pyx_SetNameInClass(__pyx_t_3, __pyx_n_s_init, __pyx_t_7) < 0) __PYX_ERR(1, 536, __pyx_L1_error)
      ^
../../../python/smt_switch/smt_switch_imp.pxi:872:38: note: expanded from macro '__Pyx_SetNameInClass'
    (likely(PyDict_CheckExact(ns)) ? _PyDict_SetItem_KnownHash(ns, name, value, ((PyASCIIObject *) name)->hash) : PyObject_SetItem(ns, name, value))

This was fixed in cython/cython@fd96443, first included in version 3.0.5. We use an ancient version, I updated it to be at least this.