Upgrade GitHub Actions for Node 24 compatibility

[ko3n1g]

What does this PR do ?

This builds upon #2677 and solves the workflow issue by also bumping the actions/checkout in the test action.yml file.

Contribution process

Pre-checks

• I have added relevant unit tests
• I have added relevant functional tests
• I have added proper typing to my code Typing guidelines
• I have added relevant documentation
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[github-actions]

This PR has been automatically converted to draft because all PRs must start as drafts.

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[ko3n1g]

/ok to test

[ko3n1g]

/ok to test

[svcnvidia-nemo-ci]

🔄 Merge queue validation started!

You can track the progress here: https://github.com/NVIDIA/Megatron-LM/actions/runs/23007940387