Update build image in release/6.0 (#3329)

Author: dreddy-work

eng/jobs/prepare-signed-artifacts.yml

@@ -8,7 +8,7 @@ jobs:
   dependsOn: ${{ parameters.dependsOn }}
   pool:
     name: NetCore1ESPool-Svc-Internal
-    demands: ImageOverride -equals build.windows.10.amd64.vs2019
+    demands: ImageOverride -equals windows.vs2019.amd64
   # Double the default timeout.
   timeoutInMinutes: 120
   workspace:

eng/jobs/windows-build.yml

@@ -14,8 +14,7 @@ jobs:
     pool:
       # Use a hosted pool when possible.
       ${{ if eq(variables['System.TeamProject'], 'public') }}:
-        name: NetCore-Svc-Public
-        demands: ImageOverride -equals windows.vs2019.amd64.open
+        vmImage: 'windows-2019'
       ${{ if ne(variables['System.TeamProject'], 'public') }}:
         name: NetCore1ESPool-Svc-Internal
         demands: ImageOverride -equals windows.vs2019.amd64