Updated the documentation to use the new workflow

As per Jeff's request, I've update the documentation to use a more detailed workflow on how to remove NuGet Package Restore.
Suggested new text:

> If the solution you are trying to migrate is open in Visual Studio, then changes may be lost. Visual Studio may overwrite/ignore your changes in some cases and the NuGet extension will also try to re-enable Package Restore when it sees some projects in the solution are missing it.