fdo#73552 - Set name of CSV import sheet to something friendly

Change-Id: Ia68283947d954d648fa25356f2b95ba0ab7010aa
Reviewed-on: https://gerrit.libreoffice.org/8811
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>