fix: drop legacy convertType usages and dead instanceof flagged by phpstan

TypeConverterInterface::convertType was replaced by convertPhpType. Remove the
leftover convertType implementations in the GraphQl test fixtures, and drop a
now-always-true `instanceof Type` on a non-nullable collection value type.

Author: soyuka

src/GraphQl/Tests/Type/FieldsBuilderTest.php

@@ -485,11 +485,6 @@ public function testGetResourceObjectTypeFields(string $resourceClass, Operation
         });
 
         $typeConverter = new class implements TypeConverterInterface {
-            public function convertType(\Symfony\Component\PropertyInfo\Type $type, bool $input, Operation $rootOperation, string $resourceClass, string $rootResource, ?string $property, int $depth): GraphQLType|string|null
-            {
-                return null;
-            }
-
             public function resolveType(string $type): ?GraphQLType
             {
                 return null;

src/Serializer/AbstractItemNormalizer.php

@@ -1030,7 +1030,7 @@ private function createAndValidateAttributeValue(string $attribute, mixed $value
             // Fix a collection that contains the only one element
             // This is special to xml format only
             if ('xml' === $format && null !== $collectionValueType && (!\is_array($value) || !\is_int(key($value)))) {
-                $isMixedType = $collectionValueType instanceof Type && $collectionValueType->isIdentifiedBy(TypeIdentifier::MIXED);
+                $isMixedType = $collectionValueType->isIdentifiedBy(TypeIdentifier::MIXED);
                 if (!$isMixedType) {
                     $value = [$value];
                 }

tests/Fixtures/TestBundle/GraphQl/Type/TypeConverter.php

@@ -18,7 +18,6 @@
 use ApiPlatform\Tests\Fixtures\TestBundle\Document\Dummy as DummyDocument;
 use ApiPlatform\Tests\Fixtures\TestBundle\Entity\Dummy;
 use GraphQL\Type\Definition\Type as GraphQLType;
-use Symfony\Component\PropertyInfo\Type as LegacyType;
 use Symfony\Component\TypeInfo\Type;
 
 /**
@@ -32,22 +31,6 @@ public function __construct(private readonly TypeConverterInterface $defaultType
     {
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function convertType(LegacyType $type, bool $input, Operation $rootOperation, string $resourceClass, string $rootResource, ?string $property, int $depth): GraphQLType|string|null
-    {
-        if ('dummyDate' === $property
-            && \in_array($rootResource, [Dummy::class, DummyDocument::class], true)
-            && LegacyType::BUILTIN_TYPE_OBJECT === $type->getBuiltinType()
-            && is_a($type->getClassName(), \DateTimeInterface::class, true)
-        ) {
-            return \DateTime::class;
-        }
-
-        return $this->defaultTypeConverter->convertType($type, $input, $rootOperation, $resourceClass, $rootResource, $property, $depth);
-    }
-
     /**
      * {@inheritdoc}
      */