Refactor '.is_governed_by' in Ddr::Index::Filter to use 'id-' form of resource...
Refactor '.is_governed_by' in Ddr::Index::Filter to use 'id-' form of resource ID; relates to DDR-1597.
Valkyrie indexes admin policy ID's using Valkyrie::Persistence::Solr::ModelConverter::IDPropertyValue, which results in the 'admin_policy_id_*' Solr fields having values of the form 'id-' rather than ''.