[BUG] Records always determined to require update

[swamidass]

This script never sees records as unchanged if the index is configured not to return all attribute by default. This can be fixed by changing getRemoteIndex to this implementation:

async function  getRemoteIndex(index) {
  let hits = [];
  await index.browseObjects({
    query: '', // Empty query will match all records
    batch: batch => {
      hits = hits.concat(batch);
    },
    attributesToRetrieve: ["*"]
  })
  return hits
}

And, of course, bump the algoliasearch version to >=4 on package.json.