There may be more elegant or accurate solutions, and I think the sidebar will be more customizable in the future, but a potentially unreliable CSS solution would be:
.sidebar-section-link-wrapper:nth-last-child(2) {
display: none;
}
It targets the current position of the FAQ link parent (last element -1). Having other elements between the FAQ link and the end of the list will make the CSS selector not target the proper element anymore.
But if you’re confident this part of the list won’t change, you can go for it.