benchmarks: Don't crash on overflow in IterateData

Author: eeckstein

benchmark/single-source/IterateData.swift

@@ -29,6 +29,6 @@ public func run_IterateData(_ N: Int) {
   let data = generateData()
 
   for _ in 0...10*N {
-    _ = data.reduce(0, +)
+    _ = data.reduce(0, &+)
   }
 }