Correct new search input’s rounded corners

Author: justjanne

res/css/views/dialogs/_SpotlightDialog.scss

@@ -58,6 +58,7 @@ limitations under the License.
     .mx_SpotlightDialog_searchBox {
         margin: 0;
         border: none;
+        border-radius: 8px 8px 0 0;
         padding: $spacing-12 $spacing-16;
         border-bottom: 1px solid $system;