Incompatibility with diff 2.0.0-beta3 causes a fatal error

Problem/Motivation

After upgrading to diff 2.0.0-beta3, we encountered the following error:

PHP Fatal error: Declaration of Drupal\entity_reference_revisions\Plugin\diff\Field\EntityReferenceRevisionsFieldDiffBuilder::build(Drupal\Core\Field\FieldItemListInterface $field_items) must be compatible with Drupal\diff\FieldDiffBuilderInterface::build(Drupal\Core\Field\FieldItemListInterface $field_items): mixed

After fixing that I also got:

PHP Fatal error: Declaration of Drupal\entity_reference_revisions\Plugin\diff\Field\EntityReferenceRevisionsFieldDiffBuilder::getEntitiesToDiff(Drupal\Core\Field\FieldItemListInterface $field_items) must be compatible with Drupal\diff\FieldReferenceInterface::getEntitiesToDiff(Drupal\Core\Field\FieldItemListInterface $field_items): array

The issue is that FieldReferenceInterface was updated to include return types in the function signatures. The implementation in entity_reference_revisions does not include these signatures.

Steps to reproduce

Install diff 2.0.0-beta3 then try to view the diff between two revisions of a node.

Proposed resolution

Update the class to match the interface.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.