Fatal error on Drupal 10.6+: setAvailableNewsletterIds() no longer exists

On Drupal core 10.6.x, Simplenews 4.1.1 triggers a fatal error when rendering the Simplenews subscription block.
Drupal\Core\Field\Plugin\Field\FieldWidget\EntityReferenceAutocompleteWidget no longer exposes setAvailableNewsletterIds().
SubscriptionsBlockForm::form() still calls this method via the form display renderer, causing a fatal error.
This happens on a clean Drupal 10.6.2 install with Simplenews 4.1.1 when the Simplenews Subscription block is enabled.

Steps to reproduce
1. Install Drupal core 10.6.2
2. Install Simplenews 4.1.1
3. Place the “Simplenews Subscription” block
4. Load a page containing the block

Actual result
Fatal error:
Call to undefined method
Drupal\Core\Field\Plugin\Field\FieldWidget\EntityReferenceAutocompleteWidget::setAvailableNewsletterIds()

Attaching proposed patch, needs review, I'm a newb.