Release creating NuGet packages on the fly feature

What does this MR do and why?

In Publish nuget packages on the fly (!176359 - merged), we implemented publishing NuGet packages on the fly behind a feature flag. The feature is globally enabled on gitlab.com for a week now without any issues.

In this MR, we clean up the feature flag and release the feature.

References

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• Publish nuget packages on the fly (!176359 - merged)

MR acceptance checklist

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Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Related to #509970 (closed)