PHILADELPHIA — Absence is said to make the heart grow fonder. That certainly applies to Raymond Felton, who made his return to the Knicks lineup last night against the 76ers after missing 12 games with a broken right pinkie. In his absence, the Knicks looked like a vulnerable team, a team that has more flaws than were noticed when he was in the lineup. In his absence, the Knicks looked slower and older. Their pick-and-roll game wasn’t as crisp, and they couldn’t make as many 3-point shots.