CHICAGO — William Howard Schuman wrote Le fosse Ardeatine in 1968. Schuman, an American composer, created his 9th symphony (of 10) to commemorate the March 24, 1944 mass murder of 335 Italians by German troops at the Ardeatine Caves outside Rome. Opening a Feb. 21-23 program at Symphony Center, this weekend’s performances of Schuman’s Symphony no. 9 are the first by the Chicago Symphony…