Merge pull request #20591 from dotnet-maestro-bot/merge/release/5.0-preview3-to-master

[automated] Merge branch 'release/5.0-preview3' => 'master'

.azure/pipelines/ci.yml

@@ -177,8 +177,7 @@ stages:
                 -noBuildDeps
                 $(_BuildArgs)
                 $(_InternalRuntimeDownloadArgs)
-        # Disabled until 3.1.3 is released
-        condition: false
+        condition: ne(variables['Build.Reason'], 'PullRequest')
         displayName: Build SiteExtension
 
       # This runs code-signing on all packages, zips, and jar files as defined in build/CodeSign.targets. If https://github.com/dotnet/arcade/issues/1957 is resolved,