Note that Leviticus 20:11 likewise indicates that a man who sleeps with his fathers wife must be put to death. But thats not what happened to the man who committed incest with his fathers wife in 1 Corinthians 5. Just as Matthew 18:15-17 shows us that Jesus taught that a congregation is not to have anything to do with unrepentant sinners, Paul accordingly told the Corinthians church to expel the sexual offender from the congregation instead of killing him.
So thanks to Jesus' death and resurrection, New Testament churches evidently handle sexual offenders differently than the ancient Israelites were commanded to.
Handled differently, yes, but not considered no longer a sin one should repent of.