PLT-5118 moving to last_picture_update for the profile img (#4985)

webapp/components/sidebar_header.jsx

@@ -59,7 +59,7 @@ export default class SidebarHeader extends React.Component {
             profilePicture = (
                 <img
                     className='user__picture'
-                    src={Client.getUsersRoute() + '/' + me.id + '/image?time=' + me.update_at}
+                    src={Client.getUsersRoute() + '/' + me.id + '/image?time=' + me.last_picture_update}
                 />
             );
         }