message: Increase supported LSTM version to v4.
  v4 adds the asymmetric_quantize_inputs flag. In the hybrid TFLite CPU implementation this flag controls the on-the-fly quantization. In the GPU delegate all calculations are floating point, so this is not relevant.
diff: @@ -995,7 +995,7 @@ class LSTMOperationParser : public TFLiteOperationParser {
  absl::Status IsSupported(const TfLiteContext* context,
  const TfLiteNode* tflite_node,
  const TfLiteRegistration* registration) final {
  - RETURN_IF_ERROR(CheckMaxSupportedOpVersion(registration, 3));
  + RETURN_IF_ERROR(CheckMaxSupportedOpVersion(registration, 4));
  const TfLiteLSTMParams* tf_options;
  RETURN_IF_ERROR(RetrieveBuiltinData(tflite_node, &tf_options));
  switch (tf_options->kernel_type) {
  