docs: fix typo in `authoring content.md` (#408)

Ben Schlegel

2023-08-24 9d2340e90b55fb9480e0901bc7360f3d72e688da

 quartz/styles/base.scss

@@ -320,7 +320,6 @@
  border-radius: 5px;
  overflow-x: auto;
  border: 1px solid var(--lightgray);
  position: relative;

  &:has(> code.mermaid) {
    border: none;