rephrase comments in cython_metaclass.h

Author: infmagic2047

src/sage/cpython/cython_metaclass.h

@@ -53,9 +53,10 @@ static CYTHON_INLINE int Sage_PyType_Ready(PyTypeObject* t)
         return r;
 
 #if PY_VERSION_HEX >= 0x03050000
-    // Cython 3 sets Py_TPFLAGS_HEAPSIZE before calling PyType_Ready,
-    // and resets just after the call. We need to do the same, or it may
-    // end up with illegal memory accesses.
+    // Cython 3 sets Py_TPFLAGS_HEAPTYPE before calling PyType_Ready,
+    // and resets just after the call. We need to reset it earlier,
+    // since otherwise the call to metaclass.__init__ below may have
+    // illegal memory accesses.
     // See also:
     // https://github.com/cython/cython/issues/3603
     t->tp_flags &= ~Py_TPFLAGS_HEAPTYPE;