updating pipelines to ubuntu-20.04

Author: capfei

azure-pipelines.yml

@@ -4,7 +4,7 @@
 # https://docs.microsoft.com/azure/devops/pipelines/languages/javascript
 
 pool:
-  vmImage: 'ubuntu-18.04'
+  vmImage: 'ubuntu-20.04'
 
 steps:
   - task: NodeTool@0