Validate slug for all SpecialistDocument types
Validate slug for all SpecialistDocument types

..not just the one with a format of specialist-document. Since we have now introduced more types of document lets pull the document types from the FORMATS_BY_DEFAULT_OWNING_APP mappings and remove the ones we don't need.

dinuksha/Test,dinuksha/Test,alphagov/govuk_content_models