message: Fix style of `hide-readme-header` on GitHub Enterprise
diff: .repository-content #readme:not(.blob) .Box-header {
  margin-bottom: -40px;
  + background-color: transparent !important; /* GHE #4137 */
  + border-bottom: none; /* GHE #4137 */
  }
  .repository-content #readme:not(.blob) .Box-header .btn-octicon {
  