WASHINGTON — Rep. Steve Scalise, the No. 2 House Republican, returned to the U.S. Capitol on Thursday for the first time since being diagnosed with a blood cancer known as multiple myeloma and told reporters his chemotherapy treatment is underway.“It’s kind of a few months process. They don’t know yet how long it’s going to be — four months, six months — but they want to continue to evaluate and say, ‘OK, how’s he doing? How’s the treatment?’ The treatments …