Not able to select variants in manyToOneRelation

[bramstroker]

Expected behavior

In the search grid I need to have a choice between Object and Variant and All types.

Actual behavior

Only Object option is available in the types dropdown.
The issue seems to be related to the allow Objets checkbox in the manyToOneRelation settings.
See also manyToOneRelation.js:openSearchEditor().
In pimcore 5 I was able to select variants, but this broke in pimcore 6.

Steps to reproduce

• Go to classes configuration and open a class.
• Create a new manyToOneRelation field
• Check the box allow Objects and select a class to be allowed
• Go to an object and click the search icon (loop) in the relation grid.