schemas/vegbien.sql: taxonconcept: Merged taxonconcept_unique_within_creator_by_name unique index into taxonconcept_unique_within_parent, placed parent_id first, and removed index condition, so that this index can be used as a lookup index by taxonconcept_update_ancestors() (which requires no index condition in order to apply to all taxonconcepts) in addition to as a unique index. Note that an index condition should not be necessary for the index's uniquifying task, because if a set of taxonconcepts provides only the identifyingtaxonomicname, that should collide in the taxonconcept_unique_within_creator_by_identifying_name unique index before this index collides. This assumes that the collision order when multiple indexes collide is alphabetical by the index name.