Add future-notice comment

Author: sizmailov

include/pybind11/detail/class.h

@@ -89,11 +89,14 @@ inline PyTypeObject *make_static_property_type() {
     if (PyType_Ready(type) < 0) {
         pybind11_fail("make_static_property_type(): failure in PyType_Ready()!");
     }
+
 #    if PY_VERSION_HEX >= 0x030C0000
+    // PRE 3.12 FEATURE FREEZE. PLEASE REVIEW AFTER FREEZE.
     // Since Python-3.12 property-derived types are required to
     // have dynamic attributes (to set `__doc__`)
     enable_dynamic_attributes(heap_type);
 #    endif
+
     setattr((PyObject *) type, "__module__", str("pybind11_builtins"));
     PYBIND11_SET_OLDPY_QUALNAME(type, name_obj);