Use chain.from_iterable in parsers/xlsx.py (#334)
Use chain.from_iterable in parsers/xlsx.py (#334)

Co-authored-by: roll <7f7889bab81b66af11b39dac388e6e0e003a6680@users.noreply.github.com>
okfn/datatable-py,frictionlessdata/tabulator-py,okfn/tabulator-py,frictionlessdata/tabulator-py