Delete neural_network/gan.py_tf

[priya-sundaram-dev]

Describe your change:

Deletes the obsolete neural_network/gan.py_tf file. It is a TensorFlow/Keras
implementation that was renamed to .py_tf so it is no longer collected by the
test suite, and it depends on the keras/tensorflow stack we are removing from
the repository. Nothing in the repo imports it.

Focused single-file follow-up to the cleanup discussed in #15418, per @cclauss's request.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one issue, please mention the issue number here. This PR is a follow-up to Should we remove dependencies keras and tensorflow? #15418.

[algorithms-keeper]

Closing this pull request as invalid

@priya-sundaram-dev, this pull request is being closed as the files submitted contains an invalid extension. This repository only accepts Python algorithms. Please read the Contributing guidelines first.

Invalid files in this pull request: neural_network/gan.py_tf

[priya-sundaram-dev]

Heads-up @cclauss: algorithms-keeper auto-closed this as "invalid extension" because it flags neural_network/gan.py_tf even though the PR deletes it (the bot's file-extension check doesn't distinguish added vs. removed paths). So this last bit of the #15418 cleanup can't land through a normal contributor PR.

Two low-effort options:

1. A maintainer deletes gan.py_tf directly (it's already uncollected, nothing imports it), or
2. I fold the deletion into Remove tensorflow/keras files and the keras dependency #15420 — but that risks the keeper auto-closing that PR too, so I'd rather not jeopardize the main removal.

Happy to do whatever you prefer; leaving #15420 (the actual tf/keras removal) untouched for now.