Automated agent pool migration

Signed-off-by: yijingyan2 <[email protected]>

Author: yijingyan2

.azure-pipelines/build-template.yml

@@ -38,7 +38,7 @@ jobs:
     ${{ if ne(parameters.pool, 'default') }}:
       name: ${{ parameters.pool }}
     ${{ if eq(parameters.pool, 'default') }}:
-      vmImage: 'ubuntu-20.04'
+      vmImage: 'ubuntu-latest'
 
   container:
     image: sonicdev-microsoft.azurecr.io:443/${{ parameters.sonic_slave }}:latest