add back z index css class (#275)

Signed-off-by: Andy Reding <[email protected]>

Author: areding99

src/components/ResultPanel/ResultDisplay.tsx

@@ -190,6 +190,7 @@ function RenderedResult({result, source}: RenderedResultProps) {
   if (renderer) {
     return (
       <DOMElement
+        className="malloy-render_result-wrapper"
         element={renderer}
         style={{overflow: 'hidden', height: '100%'}}
       />