rustdoc: remove unused CSS #sidebar-filler

This hack was removed in 6a5f8b1, but the
CSS was left in.

Author: notriddle

src/librustdoc/html/static/css/rustdoc.css

@@ -1804,21 +1804,6 @@ in storage.js
 		display: block;
 	}
 
-	/* Because of ios, we need to actually have a full height sidebar title so the
-	 * actual sidebar can show up. But then we need to make it transparent so we don't
-	 * hide content. The filler just allows to create the background for the sidebar
-	 * title. But because of the absolute position, I had to lower the z-index.
-	 */
-	#sidebar-filler {
-		position: fixed;
-		left: 45px;
-		width: calc(100% - 45px);
-		top: 0;
-		height: 45px;
-		z-index: -1;
-		border-bottom: 1px solid;
-	}
-
 	#main-content > details.rustdoc-toggle > summary::before,
 	#main-content > div > details.rustdoc-toggle > summary::before {
 		left: -11px;