Drop legacy document columns and approver tables

The title, classification, and document_type columns have been moved to
document_versions. The document_approvers and document_version_approvers
tables have been replaced by approval quorums and decisions.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/coredata/migrations/20260407T120000Z.sql

@@ -12,7 +12,6 @@
 -- OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 -- PERFORMANCE OF THIS SOFTWARE.
 
--- TODO: drop the title column from documents.
 ALTER TABLE documents ALTER COLUMN title DROP NOT NULL;
 
 ALTER TABLE documents DROP COLUMN description;