Update postgresql instructions (#343)

Postgres 15 does not allow creation of tables in `public` (default)  schema without  super-user access rights. `crowdsec` has to be made the owner of the public schema first. See https://stackoverflow.com/questions/74110708/postgres-15-permission-denied-for-schema-public

crowdsec-docs/docs/local_api/database.md

@@ -45,6 +45,7 @@ Connect to your `PostgreSQL` server and run the following commands:
 ```
 postgres=# CREATE DATABASE crowdsec;
 postgres=# CREATE USER crowdsec WITH PASSWORD '<password>';
+postgres=# ALTER SCHEMA public owner to crowdsec;
 postgres=# GRANT ALL PRIVILEGES ON DATABASE crowdsec TO crowdsec;
 ```