Fix doctest for `TFDeiTForImageClassification`
# What does this PR do?

Since TF 2.10, `tf.random.set_seed` with a fixed seed won't give the same model weights anymore. See the [release note](https://github.com/tensorflow/tensorflow/releases/tag/v2.10.0). We need `tf.keras.utils.set_random_seed()` for this purpose.

This PR fixes the doctest for `TFDeiTForImageClassification` by using the above solution.

- I have to update the expected value however.
- I get the new expected value on a CPU VM. It should work on the GPU VM too, but let's keep an eye on the CI result.


> LGTM! 👍
> 
> is the line that sets the non-Keras seed still needed? (`>>> tf.random.set_seed(3)`)

No we don't need it :-) Removed it.<|||||>_The documentation is not available anymore as the PR was closed or merged._