updated gatk docker to 4.2.0.0 (#60)

Author: bshifaw

haplotypecaller-gvcf-gatk4.wdl

@@ -39,7 +39,7 @@ workflow HaplotypeCallerGvcf_GATK4 {
 
     Boolean make_gvcf = true
     Boolean make_bamout = false
-    String gatk_docker = "us.gcr.io/broad-gatk/gatk:4.1.9.0"
+    String gatk_docker = "us.gcr.io/broad-gatk/gatk:4.2.0.0"
     String gatk_path = "/gatk/gatk"
     String gitc_docker = "us.gcr.io/broad-gotc-prod/genomes-in-the-cloud:2.4.7-1603303710"
     String samtools_path = "samtools"