API reference - Remove Microsoft.ML prefix from samples' namespace

[shmoradims]

Currently the samples are written like this:

namespace **Microsoft.ML**.Samples.Dynamic.*
{ 
}

This is causing the samples to not require using Microsoft.ML. We want to drop the Microsoft.ML prefix from samples and write them like this:

namespace Samples.Dynamic.*
{ 
}

[codemzs]

I fixed for all the samples and checked-in my change.