Update Directory.Build.props

Author: Bertk

Directory.Build.props

@@ -18,6 +18,7 @@
     <NoWarn>$(NoWarn);NU1507;NU5105;CS1591;NU1608</NoWarn>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <RestoreSources>
+      https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-libraries/nuget/v3/index.json
       https://api.nuget.org/v3/index.json;
     </RestoreSources>
     <!--<UsingMicrosoftArtifactsSdk>true</UsingMicrosoftArtifactsSdk>-->