fix: i18ze a string (#3210)

Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/3210
Reviewed-by: konrad <k@knt.li>
Co-authored-by: WofWca <wofwca@protonmail.com>
Co-committed-by: WofWca <wofwca@protonmail.com>

src/components/tasks/partials/singleTaskInList.vue

@@ -242,7 +242,7 @@ async function markAsDone(checked: boolean) {
 				t('task.doneSuccess') :
 				t('task.undoneSuccess'),
 		}, [{
-			title: 'Undo',
+			title: t('task.undo'),
 			callback: () => undoDone(checked),
 		}])
 	}