Five reference fields are shown twice when ERwH is installed

To reproduce the issue:

1. Perform a fresh install of Drupal 9 using standard install profile
2. Install the latest version entity_reference_hierarchy
3. Visit /admin/structure/types/manage/article/fields/add-field
4. In the 'Add new field' select list, under the 'Reference' section, see that there are two entries for 'Content', 'Taxonomy term', and 'User' entity types.

This issue is stemming from the core change that introduced "preconfigured fields" back in D8. See https://www.drupal.org/project/drupal/issues/2446511 → .

Since ERwH is dependent on entity_reference_revisions, but not overriding the getPreconfiguredOptions() method, ERwH is picking up the preconfigured field settings from ERR, which cause these "duplicate" fields.

Attaching patch for convenience/composer purposes.

Thanks @coderdan.

Using D9.5.11 with entity_reference_hierarchy 1.0 beta3:
at first glance this patch seems to work with no side effects.

Will report back if I find any issues.
J.