Remove "Runtime" namespace from example code

[justinormont]

In dotnet/machinelearning#1956, we removed Runtime from the namespaces.

Now we have to update the example code.

For example, we moved:

• Microsoft.ML.Runtime.Data to Microsoft.ML.Data
• Microsoft.ML.Runtime.TimeSeriesProcessing to using Microsoft.ML.TimeSeriesProcessing
• Microsoft.ML.Runtime.Learners to Microsoft.ML.Learners

I currently see 81 hits to ML.Runtime in the machinelearning-samples repo.

cc: @JRAlexander, @codemzs

[prathyusha12345]

This was fixed already. Closing it.