rustdoc: simplify mobile item-table CSS

Using flexbox in column direction is needlessly complicated, since no
special flex powers are being used here. Just use regular block layout.

This should result in no visible changes.

Author: notriddle

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

@@ -1870,16 +1870,9 @@ in storage.js
 	}
 
 	/* Display an alternating layout on tablets and phones */
-	.item-table {
+	.item-table, .item-row, .item-left, .item-right {
 		display: block;
 	}
-	.item-row {
-		display: flex;
-		flex-flow: column wrap;
-	}
-	.item-left, .item-right {
-		width: 100%;
-	}
 
 	/* Display an alternating layout on tablets and phones */
 	.search-results > a {