Fix use of deprecated jax_platform_name

[Prince213]

This PR fixes the following error:

______ BackendsTest.test_no_backend_warning_on_cpu_if_platform_specified _______
[gw0] linux -- Python 3.12.11 /nix/store/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-python3-3.12.11/bin/python3.12

self = <tests.api_test.BackendsTest testMethod=test_no_backend_warning_on_cpu_if_platform_specified>

    @unittest.skipIf(not sys.executable, "test requires sys.executable")
    @jtu.run_on_devices("cpu")
    def test_no_backend_warning_on_cpu_if_platform_specified(self):
      warning_not_expected = (
        "import jax; "
        "jax.config.update('jax_platform_name', 'cpu'); "
        "jax.numpy.arange(10)")

      result = subprocess.run([sys.executable, '-c', warning_not_expected],
                              check=True, capture_output=True)
>     assert "may be present" not in result.stderr.decode()
E     AssertionError: assert 'may be present' not in 'ERROR:2025-...ck to cpu.\n'
E
E       'may be present' is contained here:
E         VIDIA GPU may be present on this machine, but a CUDA-enabled jaxlib is not installed. Falling back to cpu.
E       ?           ++++++++++++++

tests/api_test.py:7632: AssertionError
=========================== short test summary info ============================
FAILED tests/api_test.py::BackendsTest::test_no_backend_warning_on_cpu_if_platform_specified - AssertionError: assert 'may be present' not in 'ERROR:2025-...ck to cpu.\n'

  'may be present' is contained here:
    VIDIA GPU may be present on this machine, but a CUDA-enabled jaxlib is not installed. Falling back to cpu.
  ?           ++++++++++++++
========= 1 failed, 29959 passed, 20204 skipped in 2379.18s (0:39:39) ==========

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[gemini-code-assist]

Summary of Changes

Hello @Prince213, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses the use of a deprecated JAX configuration setting within a test file. It updates the jax.config.update call to use the currently supported jax_platforms key instead of the older jax_platform_name, ensuring the test remains functional and aligned with modern JAX library practices. This is a maintenance fix to prevent potential warnings or errors related to deprecated features.

Highlights

• JAX Configuration Update: Replaced the deprecated jax_platform_name configuration key with the current jax_platforms within a test case to ensure compatibility with the latest JAX API.

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[gemini-code-assist]

Code Review

This pull request correctly replaces the deprecated jax_platform_name configuration option with the new jax_platforms option in a test case. The change is straightforward and helps keep the codebase up-to-date by removing usage of deprecated APIs. The implementation is sound, and I have no further comments.

[superbobry]

Thanks!

[superbobry]

Can you sign the CLA, please? I'm afraid we won't be able to merge the PR otherwise.

[Prince213]

The test failures look like they were false positives before, as the flag isn't actually respected.