update agent vm image in pipeline yml (#16467)

Author: raych1

.azure-pipelines/azure-pipelines-data-container.yml

@@ -7,7 +7,7 @@ schedules:
   always: true
 
 pool:
-  vmImage: 'Ubuntu-16.04'
+  vmImage: 'Ubuntu-20.04'
 
 variables:
   IMAGE_TAG_PREFIX: $[format('1.0.{0:HHm}', pipeline.startTime)]