Fix wrong warning message info

PiperOrigin-RevId: 554629697

python/google/protobuf/internal/python_message.py

@@ -1364,8 +1364,8 @@ def _Clear(self):
 def _UnknownFields(self):
   warnings.warn(
       'message.UnknownFields() is deprecated. Please use the add one '
-      'feature message_factory.UnknownFieldSet(message) in '
-      'message_factory.py instead.'
+      'feature unknown_fields.UnknownFieldSet(message) in '
+      'unknown_fields.py instead.'
   )
   if self._unknown_field_set is None:  # pylint: disable=protected-access
     # pylint: disable=protected-access

python/google/protobuf/pyext/message.cc

@@ -2370,8 +2370,8 @@ static PyObject* GetExtensionDict(CMessage* self, void *closure) {
 static PyObject* GetUnknownFields(CMessage* self) {
   PyErr_Warn(nullptr,
              "message.UnknownFields() is deprecated. Please use the "
-             "add one feature message_factory.UnknownFieldSet(message) in "
-             "message_factory.py instead.");
+             "add one feature unknown_fields.UnknownFieldSet(message) in "
+             "unknown_fields.py instead.");
   if (self->unknown_field_set == nullptr) {
     self->unknown_field_set = unknown_fields::NewPyUnknownFields(self);
   } else {