By Tassilo Hummel, Alasdair Pal and Steve Holland PARIS (Reuters) – French authorities seized four cargo vessels and one luxury yacht linked to oligarchs as the United States and other governments ramped up sanctions on Russia’s super-rich on Thursday over Moscow’s invasion of Ukraine. Customs officials seized the yacht of Rosneft boss Igor Sechin, who is on the U.S. and EU sanctions lists, before it attempted to flee a French Riviera port, the French finance minister said. At least five other superyachts owned by Russian billionaires are anchored or cruising in the Maldives, an Indian Ocean i…