Change `tf.keras.mixed_precision.experimental` to `tf.keras.mixed_precision`
Change `tf.keras.mixed_precision.experimental` to `tf.keras.mixed_precision`

The `tf.keras.mixed_precision.experimental` API has been removed. The non-experimental symbols under `tf.keras.mixed_precision` have been available since TensorFlow 2.4 and should be used instead.
tensorflow/docs-l10n