6869: Fix FieldCollection::new() removed in EasyAdmin 5.x

Use plain constructor instead of the removed static factory method,
fixing PHPStan staticMethod.notFound errors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: turegjorup

src/Trait/ExportCrudControllerTrait.php

@@ -47,7 +47,7 @@ public function export(AdminContext $context): Response
 
         assert($this instanceof AbstractCrudController);
         // Lifted from self::index().
-        $fields = FieldCollection::new($this->configureFields(Crud::PAGE_INDEX));
+        $fields = new FieldCollection($this->configureFields(Crud::PAGE_INDEX));
         $context->getCrud()->setFieldAssets($this->getFieldAssets($fields));
         $filters = $this->filterFactory->create($context->getCrud()->getFiltersConfig(), $fields,
             $context->getEntity());