DX: fix phpstan errors

src/Bundle/ChillThirdPartyBundle/Form/Type/PickThirdPartyTypeCategoryType.php

@@ -88,22 +88,12 @@ class PickThirdPartyTypeCategoryType extends \Symfony\Component\Form\AbstractTyp
         return ChoiceType::class;
     }
 
-    public function reverseTransform($value)
+    private function reverseTransform($value)
     {
         if (null === $value) {
             return null;
         }
 
-        if (is_array($value)) {
-            $r = [];
-
-            foreach ($value as $v) {
-                $r[] = $this->transform($v);
-            }
-
-            return $r;
-        }
-
         if ($value instanceof ThirdPartyCategory) {
             return 'category:' . $value->getId();
         }