README: use the rigth user for db access

Only kcidb_editor has the right permission.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>

Author: padovan

README.md

@@ -163,7 +163,7 @@ docker logs postgres
 ### Connecting to the Database
 
 ```bash
-docker exec -it postgres psql -U kcidb -d kcidb
+docker exec -it postgres psql -U kcidb_editor -d kcidb
 ```
 
 ### Authentication