Fix phpcs standards.

modules/custom_field_graphql/src/Plugin/GraphQLCompose/FieldType/CustomFieldItem.php

@@ -106,6 +106,7 @@ class CustomFieldItem extends GraphQLComposeFieldTypeBase implements FieldProduc
    *   The field context.
    * @param \Drupal\Core\Entity\EntityInterface|null $reference
    *   The referenced entity if applicable.
+   *
    * @return mixed
    *   The value of the subfield.
    */
@@ -255,13 +256,13 @@ class CustomFieldItem extends GraphQLComposeFieldTypeBase implements FieldProduc
   /**
    * The GraphQL union type for this field (non generic).
    *
-   * @param $subfield
+   * @param string $subfield
    *   The name of the subfield.
    *
    * @return string
    *   Type in format of {Entity}Union
    */
-  public function getUnionTypeSdl($subfield): string {
+  public function getUnionTypeSdl(string $subfield): string {
     $settings = $this->getFieldDefinition()->getSettings();
     $custom_items = $this->customFieldManager->getCustomFieldItems($settings);
     $custom_item = $custom_items[$subfield];