rustdoc: remove unnecessary CSS .search-results { clear: both }

Since the tabs use flexbox instead of float as of
44d9b8d070, clearing does nothing.

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

@@ -880,8 +880,6 @@ so that we can apply CSS-filters to change the arrow color in themes */
 
 .search-results.active {
 	display: block;
-	/* prevent overhanging tabs from moving the first result */
-	clear: both;
 }
 
 .search-results .desc > span {