From Wikimedia Foundation Governance Wiki
.wmf-collapsible-box-container .wmf-collapsible-box-title {
flex: 8;
font-family: 'Georgia';
font-style: normal;
font-weight: 400;
font-size: 1.5rem;
color: #202122;
margin-bottom: 12px;
}
.wmf-collapsible-box-container .mw-collapsible-toggle:before,
.wmf-collapsible-box-container .mw-collapsible-toggle:after{
display: none;
}
.wmf-collapsible-box-container .mw-collapsible-toggle {
flex: 2;
display: flex;
justify-content: flex-end;
width: 24px;
height: 24px;
margin-top: -40px;
}
.wmf-collapsible-box-container .mw-collapsible-text {
color: transparent;
background-repeat: no-repeat;
background-position: center;
background-image: url("https://upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Collapse.svg/24px-Collapse.svg.png");
}
.wmf-collapsible-box-container .mw-collapsed .mw-collapsible-text {
color: transparent;
background-image: url("https://upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Expandarrow.svg/24px-Expandarrow.svg.png");
}
.wmf-collapsible-box-container .wmf-collapsible-box-content {
font-family: 'Georgia';
font-size: 1.125rem;
line-height: 175%;
color: #202122;
}