Case C-387/19: Judgment of the Court (Fourth Chamber) of 14 January 2021 (request for a preliminary ruling from the Raad van State — Belgium) — RTS infra BVBA, Aannemingsbedrijf Norré-Behaegel BVBA v Vlaams Gewest (Reference for a preliminary ruling — Public procurement contracts — Directive 2014/24/EU — Article 57(6) — Optional grounds for exclusion — Measures taken by the economic operator to demonstrate its reliability despite the existence of an optional ground for exclusion — Obligation of the economic operator to provide evidence of such measures on its own initiative — Direct effect)