Rename deprecated call to experimental_distribute_datasets_from_function

[swap-10]

tf.distribute.Strategy.experimental_distribute_datasets_from_function was deprecated and replaced with tf.distribute.Strategy.distribute_datasets_from_function in the 2.4.0 release.
See 2.4.0 release notes -> breaking changes -> tf.distribute.

This PR replaces the call to this deprecated method with the appropriate renamed method in the tpu guide notebook.

[github-actions]

Preview

Preview and run these notebook edits with Google Colab:

• site/en/guide/tpu.ipynb

Rendered notebook diffs available on ReviewNB.com.

Format and style

Use the TensorFlow docs notebook tools to format for consistent source diffs and lint for style:

$ python3 -m pip install -U --user git+https://github.com/tensorflow/docs

$ python3 -m tensorflow_docs.tools.nbfmt notebook.ipynb

$ python3 -m tensorflow_docs.tools.nblint --arg=repo:tensorflow/docs notebook.ipynb

If commits are added to the pull request, synchronize your local branch: git pull origin tpu-guide-rename-deprecated-fn