updateIndex (record, opts) {
    opts || (opts = {})
    this.getIndex(opts.index).updateRecord(record)
  }
Update a record's position in a single index of this collection. See
{@link Collection#updateIndexes} to update a record's position in all
indexes at once.

@method Collection#updateIndex
@since 3.0.0
@param {object} record The record to update.
@param {object} [opts] Configuration options.
@param {string} [opts.index] The index in which to update the record's
position. If you don't specify an index then the record will be updated
in the main index.