Issue #3258371 by nod_, Wim Leers: fix yarn vendor-update command

  // Use Array.reduce for sequential processing to avoid corrupting the

  // contents of the concatenated CKEditor 5 translation files.

  process.reduce(async (previous, { pack, files = [], folder = false, library = false }) => {

  await process.reduce(async (previous, { pack, files = [], folder = false, library = false }) => {

    return previous.then(async () => {

      const sourceFolder = pack;

      const libraryName = library || folder || pack;