Fix Type issues

macs2.wdl

@@ -5,10 +5,10 @@ import "common.wdl"
 task PeakCalling {
     input {
         String? preCommand
-        File inputBams
-        File inputBamsIndex
-        File? controlBams
-        File? controlBamsIndex
+        Array[File]+ inputBams
+        Array[File]+ inputBamsIndex
+        Array[File]+? controlBams
+        Array[File]+? controlBamsIndex
         String outDir
         String sampleName
         Int threads = 1