At least publicly, Mitchell Robinson isn’t holding a grudge against Joel Embiid. When the Knicks and the 76ers met in the playoffs two years ago, Embiid’s flagrant foul, in which he grabbed Robinson’s left leg while he was airborne, eventually cut Robinson’s postseason short. Then-teammate Donte DiVincenzo called it a dirty play. Asked about it Sunday, Robinson took the high road. “I don’t [think he’s a dirty player]. I really don’t live in the past,” he said, as the Knicks prepared to host the 76ers for Game 1 of the second-round series. “It is what it is. I just move on.” Robinson is focused on slowing down the superstar center and helping the Knicks return to the Eastern Conference finals. He will have a major role, not only defending Embiid, but as one of the key pieces to the Knicks defense overall. In the opening-round series against the Hawks, the 7-footer was terrific, averaging 6.2 points, 5.3 rebounds and a block in 14 minutes per game.…