message: Drop outdated CSS features
diff: @@ -18,17 +18,6 @@ markdown-toolbar > :nth-last-child(4) { /* H1, B, I */
  display: none;
  }
  -/* Add hover underline for `linkify-branch-refs` */
  -a .commit-ref:hover,
  -a .commit-ref:hover span {
  - text-decoration: underline !important;
  -}
  -
  -.commit-ref span {
  - /* The extra span on branch names interferes with a possible deletion line-through */
  - text-decoration: inherit;
  -}
  -
  /* Make tab indented code more readable on GitHub and Gist */
  * {
  -moz-tab-size: 4 !important;
  @@ -41,15 +30,6 @@ a .commit-ref:hover span {
  border-top: none !important;
  }
  -/* Multiple comment labels margin */
  -.timeline-comment .timeline-comment-label + .timeline-comment-label {
  - margin-right: -5px;
  -}
  -
  -.review-comment .timeline-comment-label + .timeline-comment-label {
  - margin-left: 5px;
  -}
  -
  /* For `open-all-selected` and `filter-pr-by-build-status`: set a reduced padding for all buttons for #1830 and #1904 */
  .table-list-filters .table-list-header-toggle .select-menu-button {
  padding-right: 8px;
  @@ -90,17 +70,6 @@ a .commit-ref:hover span {
  }
  }
  -/* Fix subpixel rendering Chrome bug in tooltips' triangles */
  -.tooltipped:hover::before,
  -.tooltipped:hover::after,
  -.tooltipped:active::before,
  -.tooltipped:active::after,
  -.tooltipped:focus::before,
  -.tooltipped:focus::after {
  - opacity: 1;
  - animation-fill-mode: backwards !important;
  -}
  -
  /* Smoothen mouse animation on 404 pages */
  .js-plaxify {
  transition: transform 0.1s;
  