Keras Improved Backend Checking

Before :

requires_trainable_backend = pytest.mark.skipif(
    backend() == "numpy" or backend() == "openvino",
    reason="Trainer not implemented for NumPy and OpenVINO backend.",
)

After :

requires_trainable_backend = pytest.mark.skipif(
    backend() in ["numpy", "openvino"],
    reason="Trainer not implemented for NumPy and OpenVINO backend.",
)

Comment From: sachinprasadhs

@FNICKE , Please create a PR with the suggested changes.

Comment From: github-actions[bot]

This issue is stale because it has been open for 14 days with no activity. It will be closed if no further activity occurs. Thank you.