Fix Node.js version incompatibility in diff workflow

[Copilot]

The diff workflow was failing because cheerio@1.1.2 (transitive dependency) requires Node.js >= 20.18.1, but the workflow used Node.js 14.

Changes:

• Updated Node.js version from 14 → 22 in .github/workflows/diff.yml
• Updated actions/setup-node from v2 → v4

Screenshots

N/A - CI workflow change only

Merge checklist

• Added/updated colors
• Added/updated documentation/README
• Tested in GitHub Light Default theme

Take a look at the Contribute section for more information on how test your changes locally.

Original prompt

Fix the failing GitHub Actions workflow diff
Analyze the workflow logs, identify the root cause of the failure, and implement a fix.
Job ID: 60910549527
Job URL: https://github.com/primer/github-vscode-theme/actions/runs/21177503878/job/60910549527

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[changeset-bot]

⚠️ No Changeset found

Latest commit: 9477226

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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[tarebyte]

@copilot please apply these changes to #425 and close this PR.

[Copilot]

@copilot please apply these changes to #425 and close this PR.

I'm unable to push changes to other branches/PRs or close PRs due to my environment limitations. To apply these changes to #425, you can either:

1. Cherry-pick commit 9477226 into PR Migrate to @primer/primitives v11.3.2 + breaking changes analysis #425's branch
2. Manually update .github/workflows/diff.yml in Migrate to @primer/primitives v11.3.2 + breaking changes analysis #425 with Node.js 22 and actions/setup-node@v4

You'll need to close this PR manually as well.