The Yankees are down another reliever. Yerry De los Santos landed on the 15-day injured list on Thursday with right elbow discomfort. The right-hander threw 14 pitches in Wednesday night’s 3-2 loss to the Los Angeles Angels, recording one out while allowing a hit and a walk. “Just felt like he wasn’t able to really extend, so he’s getting the testing done today,” manager Aaron Boone said …