Breaking: #77934 - Remove field select_key from content element preview 

See forge#77934

Description 

The value of the field select_key has been shown in the preview of a content element in the page module. This field has been removed and therefore also the preview has been removed.

Impact 

The preview of this field is not available anymore.

Affected Installations 

Every installation or third party extension which uses the field.

Migration 

No migration available.