Add missing alembic revision for ci_username/ci_password
    
    In the commit 9c6dee24463fdbfe88c21cfa4a6d7d3af87a5b7c we have added
    two fields in the database to store the username and password to use
    when authenticating to jenkins. However, we missed the corresponding
    alembic revision.
    This commit fixes this mistake.
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr></pingou@pingoured.fr>