chore: fix phpstan errors

src/Controller/Booking/Create/Step2Controller.php

@@ -132,6 +132,7 @@ class Step2Controller extends AbstractController
         }
     }
 
+    /** @param array<int, \App\Form\Model\RoomSelectionDto> $roomSelections */
     private function calculateParticipantsCount(array $roomSelections, Travel $travelData): int
     {
         $participantsCount = 0;