Remove use of the .NET 10 - UB channel

[mmitche]

The .NET 10 - UB channel was a temporary channel that was used to avoid mixing the output of the VMR with the output of traditional official builds.

I believe this can be removed now. This will involve updating all subscriptions that source from .NET 10 UB to .NET 10.0.1xx SDK and adding a default channel for .NET 10.0.1xx SDK for dotnet/dotnet.

One more thing to consider is whether to associate the 10.0.1xx branch of the VMR with both .NET 10 and .NET 10.0.1xx SDK. I think this makes sense to do, whereas 2xx+ branches will only get associated with the .NET 10.0.Nxx channel.