Remove steps_per_execution_tuning from imports

Author: Frightera

keras/engine/training.py

@@ -34,7 +34,6 @@
 from keras.engine import data_adapter
 from keras.engine import functional
 from keras.engine import input_layer as input_layer_module
-from keras.engine import steps_per_execution_tuning
 from keras.layers.activation import Softmax as SoftmaxLayer
 from keras.engine import training_utils
 from keras.metrics import base_metric