Thanks again to Volkswagen, Rivian's stock is soaring.Rivian Automotive (RIVN 11.07%) stock is wrapping up the trading week on a high note, revving 10% higher to over $18 as of 12:30 p.m. ET -- and for a most surprising reason:This morning, investment bank Mizuho raised its price target on Rivian...to$15 a share. What Mizuho said about RivianLet me repeat that: Rivian stock closed at more than $16 last night. Mizuho just said it's only worth$15 (and gave the shares only a neutral rating -- not a buy). And ...