Correct use statement. (#898)

Author: ndrake0027

src/Plugin/GraphQL/DataProducer/Field/EntityReference.php

@@ -4,7 +4,7 @@
 
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityRepositoryInterface;
-use Drupal\Core\Entity\EntityTypeManager;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Entity\FieldableEntityInterface;
 use Drupal\Core\Entity\TranslatableInterface;
 use Drupal\Core\Field\EntityReferenceFieldItemListInterface;