[Data] Move imports into TFPRedictor in batch inference example

[bveeramani]

Why are these changes needed?

We're updating our CI to use Python 3.11. Accordingly, we're updating the TensorFlow version to 2.15. To avoid test failures from #44274, this PR moves the TensorFlow imports into the TFPredictor methods.

Related issue number

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• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[bveeramani]

cc @can-anyscale

[can-anyscale]

beautiful, thank you

[c21]

Thanks for fix!