rustdoc: remove unused CSS .search-container > *

The two items it was really intended to target were the buttons, and those
both need to have the style set directly on them anyway because the buttons
are both child elements of wrappers.

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

@@ -808,9 +808,6 @@ table,
 	height: 34px;
 	margin-top: 4px;
 }
-.search-container > * {
-	height: 100%;
-}
 .search-results-title {
 	margin-top: 0;
 	white-space: nowrap;