Relax test dependencies for MLJ

[ablaom]

TimeSeriesClassification.jl/test/MiniRocket/tests.jl

Line 4 in bbf35d1

using MLJ: machine, fit!, fitted_params, transform

It doesn't look like one needs all of MLJ for testing. I think MLJBase should suffice.

If you are using any measures (metrics) from MLJ, then now that this has just merged, you will additionally need to add StatisticalMeasures.jl as a test dependency and add using StatisticalMeasures to your tests.