docs: remove out of date admonition (#2114)

Lumen Yang

2025-09-05 a4028289aae22f2a073b2837c3a85d9fc4a86087

 quartz/components/styles/readermode.scss

@@ -15,6 +15,7 @@
    width: 20px;
    height: 20px;
    top: calc(50% - 10px);
    fill: var(--darkgray);
    stroke: var(--darkgray);
    transition: opacity 0.1s ease;
  }