Revert "update filterMutectCalls memory multiplier"

This reverts commit eec323ef.

gatk.wdl

@@ -436,7 +436,7 @@ task FilterMutectCalls {
         String? extraArgs
 
         Int memory = 8
-        Float memoryMultiplier = 2
+        Float memoryMultiplier = 1.5
         String dockerImage = "quay.io/biocontainers/gatk4:4.1.2.0--1"
     }