From Acadēmīa Latīnitātis
#collapse-pre-one .mw-collapsible-toggle .up,
#collapse-pre-one.mw-collapsed .mw-collapsible-toggle .down {
display: none;
}
#collapse-pre-one .mw-collapsible-toggle .down,
#collapse-pre-one.mw-collapsed .mw-collapsible-toggle .up {
display: inline;
}