(Bloomberg) -- Vivendi SE shareholder Artisan Partners is opposing the company’s plan to sell bits of its prized asset, Universal Music Group, including a proposed deal with a blank-check firm backed by billionaire Bill Ackman.The move adds pressure on Vincent Bollore’s French media group before shareholders are set to meet on June 22 to vote on a plan to spin off 60% of the world’s biggest music company.“Selling off pieces of UMG to other investors in return for cash is a sub-optimal capital al