Improve readability in TensorFlow Keras classification tutorial

[Sunny11092003]

Improved the readability and beginner-friendliness of the Keras classification tutorial by fixing minor grammar issues, clarifying wording, and adding a helpful training comment.

[google-cla]

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[github-actions]

Preview

Preview and run these notebook edits with Google Colab:

• site/en/tutorials/keras/classification.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 patch-1