docs(Popover): fix example (react-bootstrap#5684)

Author: kyletsang

www/src/examples/Overlays/ScheduleUpdate.js

@@ -6,7 +6,7 @@ const UpdatingPopover = React.forwardRef(
     }, [children, popper]);
 
     return (
-      <Popover ref={ref} content {...props}>
+      <Popover ref={ref} body {...props}>
         {children}
       </Popover>
     );