Fixed Single-Selection Mode for the Taxonomy Chooser

The single-selection mode that is available for the taxonomy chooser component has been fixed. In addition to that, the singleSelection configuration option is autmatically derived from the maxCardinality flag of the taxonomy link list. So when the maxCardinality is set to 1 for the TaxonomyLinkListPropertyField, the dialog switches to single-selection too.

(CMS-22696)