Add CPU and GPU behavior notice and example to tf.nn.embedding_lookup function
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Title:
Add CPU and GPU Behavior Notice and Example to tf.nn.embedding_lookup Function

Description:
This pull request addresses issue #17417.

Changes Made:

Added a notice and example directly to the source code of the tf.nn.embedding_lookup function to highlight the behavior difference between CPU and GPU usage.
The added notice explains that on a GPU, out-of-bound indices result in storing a value of 0, while on a CPU, it raises an error.
Included example code that demonstrates how to use the tf.nn.embedding_lookup function for both CPU and GPU contexts.

Context:
The purpose of this contribution is to improve the documentation and provide clear guidance for users of the tf.nn.embedding_lookup function when working with CPU and GPU.

Additional Notes:
I've followed the guidelines for contributing to TensorFlow and made sure that the changes align with the project's standards.

Please review and consider merging these changes. Thank you!