fix: appease linters and psalm

Signed-off-by: Marcel Klehr <mklehr@gmx.net>

lib/private/TextToImage/Db/TaskMapper.php

@@ -25,7 +25,6 @@ declare(strict_types=1);
 
 namespace OC\TextToImage\Db;
 
-use DateTime;
 use OCP\AppFramework\Db\DoesNotExistException;
 use OCP\AppFramework\Db\Entity;
 use OCP\AppFramework\Db\MultipleObjectsReturnedException;