fix: bundle fetching with asset prefix (#63627)
Closes: https://github.com/vercel/next.js/issues/63623
When a relative assetPrefix was set (e.g. `/custom-asset-prefix`),
bundle fetching would always return a 404 as the assetPrefix was not
removed from filesystem path
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Co-authored-by: JJ Kasper <jj@jjsweb.site>
