Math.ScaleB documentation is incorrect.

https://github.com/dotnet/runtime/pull/42476 seems to have moved ScaleB from a C-runtime call to a managed implementation.\
[The documentation](https://learn.microsoft.com/en-us/dotnet/api/system.math.scaleb?view=net-8.0), however, still has a remark that the underlying C runtime is called.

Since this is no longer the case, the remark should probably be removed.