MAPG-240 add use for PlaceInChallenge (used in MapAdminController::deleteChallenge)

src/Controller/MapAdminController.php

@@ -8,6 +8,7 @@ use MapGuesser\Interfaces\Response\IContent;
 use MapGuesser\PersistentData\Model\Challenge;
 use MapGuesser\PersistentData\Model\Map;
 use MapGuesser\PersistentData\Model\Place;
+use MapGuesser\PersistentData\Model\PlaceInChallenge;
 use MapGuesser\PersistentData\PersistentDataManager;
 use MapGuesser\Repository\ChallengeRepository;
 use MapGuesser\Repository\GuessRepository;