Remove the without-path db flavor

it's not used, and keeping it makes code unnecessarly complex.

---

Migrated from D8668 (view on Phabricator)

swh/provenance/sql/upgrades/004.sql

+-- SWH provenance DB schema upgrade
+-- from_version: 3
+-- to_version: 4
+-- description: rename db flavor (without-path heving been removed)
+--              will fail if the db is using a without-path flavor.
+alter type database_flavor rename value 'with-path' to 'normalized';
+alter type database_flavor rename value 'with-path-denormalized' to 'denormalized';
+
+alter type database_flavor rename to database_flavor_old;
+
+create type database_flavor as enum (
+  'normalized',
+  'denormalized'
+);
+comment on type database_flavor is 'Flavor of the current database';
+
+drop function swh_get_dbflavor;
+
+alter table dbflavor
+  alter column flavor type database_flavor using flavor::text::database_flavor;
+
+create function swh_get_dbflavor() returns database_flavor language sql stable as $$
+  select coalesce((select flavor from dbflavor), 'normalized');
+$$;
+
+drop type database_flavor_old;