message: Correct border radius for `toggle-files-button`
diff: border: none;
  }
  +.rgh-files-hidden .Box-header {
  + border-radius: 6px;
  +}
  +
  /* Hide "Readme" link made unnecessary by this feature #3580 */
  h3.sr-only + .mt-3 .muted-link[href='#readme'] {
  display: none;
  