Improved Backend Checking

[FNICKE]

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.",
)

[sachinprasadhs]

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

[github-actions]

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.

[FNICKE]

Refactor requires_trainable_backend Condition

Description:
This PR updates the requires_trainable_backend decorator to use a more concise syntax with the in operator for checking backend values.

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

After:
python
Copy
Edit
requires_trainable_backend = pytest.mark.skipif(
backend() in ["numpy", "openvino"],
reason="Trainer not implemented for NumPy and OpenVINO backend.",
)
Why this change?
Improves readability and maintainability.

Uses a more Pythonic approach with in for multiple condition checks.

Checklist:
Code change tested and verified.

No functionality changes, only refactoring.