MediaModal: fix hotkey navigation

Fixes https://gitlab.com/soapbox-pub/soapbox/-/issues/1209

app/soapbox/features/ui/components/modals/media-modal.tsx

@@ -83,7 +83,7 @@ const MediaModal: React.FC<IMediaModal> = (props) => {
     return () => {
       window.removeEventListener('keydown', handleKeyDown);
     };
-  }, []);
+  }, [index]);
 
   const getIndex = () => {
     return index !== null ? index : props.index;