Show PageFlag (a tutorial arrow) above of other elements

frontend/src/metabase/tutorial/PageFlag.css

@@ -19,6 +19,8 @@
   line-height: 24px;
 
   transition: left 0.5s ease-in-out, top 0.5s ease-in-out;
+
+  z-index: 5;
 }
 
 .PageFlag:before,