fix action button over userlist and dropdown

bigbluebutton-html5/imports/ui/components/app/styles.scss

@@ -100,7 +100,7 @@
   @extend %text-elipsis;
   @extend %highContrastOutline;
   outline-style: solid;
-  z-index: 3;
+  z-index: 4;
   overflow: visible;
   order: 1;