BRUSSELS — Moscow’s shadow fleet is back in the EU’s crosshairs. Brussels sees the opportunity to prepare another round of sanctions against Russia, and the loose network of aging, opaquely owned tankers used to move Russian oil around the world is likely to be a key target, European diplomats and officials told POLITICO. Tightening the screws on the fleet will help choke off one of the Kremlin’s most important revenue streams — and increase pressure on Vladimir Putin to drop his maximalist