BAGHDAD — The Muslim cleric responsible for the practice of beheading hostages in Iraq — including two Americans this week — has been killed in a U.S. air strike, a newspaper and Islamic clerics said yesterday. ------------------------------ The Muslim cleric, Sheik Abu Anas Shami, 35, was killed when a missile hit the car he was traveling in on Friday in the western Baghdad suburb of Abu Ghraib, said the clerics, who have close ties to the family in Jordan. They spoke on the condition of anonymity. ----------------------------------