bpo-34902: Fixes VM image for Azure Pipelines build (GH-9719)

(cherry picked from commit 4313a293)
Co-authored-by: Steve Dower <steve.dower@microsoft.com>

.azure-pipelines/ci.yml

@@ -116,7 +116,7 @@ jobs:
   condition: and(succeeded(), eq(dependencies.Prebuild.outputs['tests.run'], 'true'))
 
   pool:
-    vmImage: vs2017-win2017
+    vmImage: vs2017-win2016
 
   strategy:
     matrix:

.azure-pipelines/pr.yml

@@ -64,7 +64,7 @@ jobs:
   condition: and(succeeded(), eq(dependencies.Prebuild.outputs['tests.run'], 'true'))
 
   pool:
-    vmImage: vs2017-win2017
+    vmImage: vs2017-win2016
 
   strategy:
     matrix: