Updated NuGet.config - add disable for msbuild bb7

Author: vseanreesermsft

NuGet.config

@@ -54,6 +54,7 @@
     <add key="darc-int-dotnet-aspnetcore-cea5fa6" value="true" />
     <!--  End: Package sources from dotnet-aspnetcore -->
     <!--  Begin: Package sources from DotNet-msbuild-Trusted -->
+    <add key="darc-pub-DotNet-msbuild-Trusted-bb7294f-1" value="true" />
     <!--  End: Package sources from DotNet-msbuild-Trusted -->
     <!--  Begin: Package sources from dotnet-emsdk -->
     <!--  End: Package sources from dotnet-emsdk -->