BUGFIX: Remove ref to obsolete ContentNegotiator::disable. See sapphire r93682
BUGFIX: Remove ref to obsolete ContentNegotiator::disable. See sapphire r93682

andrelohmann/silverstripe-googlesitemaps,silverstripe-rebelalliance/silverstripe-googlesitemaps,silverstripe-labs/silverstripe-googlesitemaps,wilr/silverstripe-googlesitemaps