8 files declare their use of EntityReferenceFieldItemListInterface in Drupal 9

EntityReferenceFieldNormalizer.php in core/modules/jsonapi/src/Normalizer/EntityReferenceFieldNormalizer.php

EntityReferenceFormatterBase.php in core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/EntityReferenceFormatterBase.php

FileMediaFormatterBase.php in core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatterBase.php

HalEntityNormalizationTrait.php in core/modules/hal/tests/src/Functional/EntityResource/HalEntityNormalizationTrait.php

ImageFormatterBase.php in core/modules/image/src/Plugin/Field/FieldFormatter/ImageFormatterBase.php

Relationship.php in core/modules/jsonapi/src/JsonApiResource/Relationship.php

ResourceIdentifier.php in core/modules/jsonapi/src/JsonApiResource/ResourceIdentifier.php

ResourceObjectNormalizer.php in core/modules/jsonapi/src/Normalizer/ResourceObjectNormalizer.php