Revert npm publish workflow runner to ubuntu-latest

[MelvinBot]

Details

Reverts runs-on for the npm publish job from blacksmith-2vcpu-ubuntu-2404 back to ubuntu-latest.

Blacksmith runners are classified as "self-hosted" by GitHub Actions, but npm publish --provenance strictly requires "github-hosted" runners for Sigstore provenance verification. This causes an E422 error when any Expensify npm package tries to publish:

npm error code E422
npm error 422 Unprocessable Entity - Error verifying sigstore provenance bundle:
Unsupported GitHub Actions runner environment: "self-hosted".
Only "github-hosted" runners are supported when publishing with provenance.

This single change fixes publishing for all repos that call this reusable workflow:
react-native-wallet, react-native-onyx, react-native-live-markdown, expensify-common, eslint-config-expensify, react-native-qrcode-svg, react-native-key-command, react-native-x-maps, react-native-x-draggable-list, and react-native-x-geolocation.

Related Issues

https://github.com/Expensify/Expensify/issues/599808

Manual Tests

Merge this PR and verify that npm publish succeeds on one of the affected repos (e.g., push a change to react-native-wallet main and confirm the publish workflow completes without E422).

Linked PRs

N/A - no downstream changes needed. All affected repos reference npmPublish.yml@main so they pick up this fix automatically.