keras input shape is now an iterate object

https://github.com/aladdinpersson/Machine-Learning-Collection/blob/558557c7989f0b10fee6e8d8f953d7269ae43d4f/ML/TensorFlow/Basics/tutorial3-neuralnetwork.py#L20

keras input shape is now an iterate object

should be replace by keras.Input(shape=(28 * 28,))