update test_tensorflow_keras_models for numpy.str deprecation

tests/models/test_tensorflow_keras_models.py

@@ -322,7 +322,7 @@ def test_save_load_with_sequence_features(self, tmpdir, loss, optimizer, metrics
         indices_a[:, 0] = np.arange(10)
         inputs_a = tf.SparseTensor(indices_a, values_a, (batch_size, timesteps, 1))
 
-        values_b = np.zeros(10, dtype=np.str)
+        values_b = np.zeros(10, dtype=str)
         indices_b = np.zeros((10, 3), dtype=np.int64)
         indices_b[:, 0] = np.arange(10)
         inputs_b = tf.SparseTensor(indices_b, values_b, (batch_size, timesteps, 1))