changed to ubuntu agent

Author: mbt1

CI/Azure-DevOps/AZ_NightlyCleanup.yml

@@ -4,7 +4,7 @@
 # https://aka.ms/yaml
 
 pool:
-  vmImage: 'vs2017-win2016'
+  vmImage: 'ubuntu-latest'
 
 schedules:
   - cron: 1 16 * * *