Use upstream reduces motion skin option

The new accessibility rules default to on, so no need to list
it in skin.json but we need to remove the now duplicated style.

Depends-On: Ie1c6c1ba7263c232d874263fdae7427a5ec489f6
Change-Id: I92f622b92adb8735c38a4ebe56eaf5bfc4ae37bf

resources/skins.vector.styles/skin.less

@@ -30,24 +30,3 @@
 @media print {
 	@import './layouts/print.less';
 }
-
-/**
- * Respect users who prefer reduced motion.
- * This code can be removed if and when it is upstreamed to ResourceLoaderSkinModule
- * (see T254399).
- */
-/* stylelint-disable declaration-no-important, time-min-milliseconds */
-@media ( prefers-reduced-motion: reduce ) {
-	*,
-	:before,
-	:after {
-		animation-delay: -1ms !important; /* 1 */
-		animation-duration: 1ms !important; /* 1 */
-		animation-iteration-count: 1 !important; /* 1 */
-		// stylelint-disable-next-line plugin/no-unsupported-browser-features
-		background-attachment: initial !important; /* 2 */
-		scroll-behavior: auto !important; /* 3 */
-		transition-delay: 0s !important; /* 4 */
-		transition-duration: 0s !important; /* 4 */
-	}
-}