message: Fix incorrect link to version compatibility
  While looking into `tensorflow/java/README.md` the
  `API stability guarantees` retured 404. This
  fix made the change `version_semantics` -> `version_compat`
  to fix the issue.
diff: # TensorFlow for Java
  > *WARNING*: The TensorFlow Java API is not currently covered by the TensorFlow
  -> [API stability guarantees](https://www.tensorflow.org/guide/version_semantics).
  +> [API stability guarantees](https://www.tensorflow.org/guide/version_compat).
  >
  > For using TensorFlow on Android refer instead to
  > [contrib/android](https://www.tensorflow.org/code/tensorflow/contrib/android),
  