Overload fit_data_scitype trait

[ablaom]

Since RFE is Unsupervised the fallback for fit_data_scitype is wrong. We need something like:

MMI.fit_data_scitype(::RecursiveFeatureElimination{M}) where M = Union{
    Tuple{input_scitype(M), target_scitype(M)},
    Tuple{input_scitype(M), target_scitype(M), AbstractVector{<:Real},
}

Sorry this is not documented in the MLJModelInterface docs, but I have opened an issue to correct this.

[ablaom]

Closing as working on a different resolution.

The problem is that you can't use RFE in a pipeline at the moment.