fix: update data-isowner when changing is ownership

fixes multiple ownership toggles

public/src/client/groups/details.js

@@ -81,6 +81,7 @@ define('forum/groups/details', [
 				case 'toggleOwnership':
 					api[isOwner ? 'del' : 'put'](`/groups/${ajaxify.data.group.slug}/ownership/${uid}`, {}).then(() => {
 						ownerFlagEl.toggleClass('invisible');
+						userRow.attr('data-isowner', isOwner ? '0' : '1');
 					}).catch(alerts.error);
 					break;