Skip MI300x8 tests since the machines are no longer available

[msaroufim]

No description provided.

[github-actions]

Coverage report

This PR does not seem to contain any modification to coverable code.

[Copilot]

Pull request overview

This PR updates the test suite to skip tests for MI300x8 GPU machines, which are no longer available. The changes ensure that tests no longer attempt to run on infrastructure that doesn't exist.

Key changes:

• Removed MI300x8 from the parametrized GPU types in test_github_launcher_python_script, leaving only NVIDIA
• Added @pytest.mark.skip decorator to test_github_launcher_multi_gpu with an appropriate reason
• Added a note in the docstring explaining why the test is skipped

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[Copilot]

The docstring states "Tests all GPU types to verify runners are working" but this test only tests MI300x8 and is now being skipped. Since the test is skipped, consider updating the docstring to clarify that this was a multi-GPU specific test for MI300x8 machines, rather than implying it tests all GPU types.

Suggested change

	Test GitHubLauncher with a real Python script using real GitHub Actions.
	Tests all GPU types to verify runners are working.
	Note: This test is skipped because MI300x8 machines are no longer available.
	Multi-GPU test of GitHubLauncher with a real Python script using real GitHub Actions,
	specifically targeting MI300x8 GitHub runners to verify they are working.
	Note: This test is currently skipped because MI300x8 machines are no longer available.