Docs are wrong about the package that owns `MacroAvg` etc

[ablaom]

According to the docs for MulticlassFScore MacroAvg is owned by StatisticalMeasuresBase.jl. While this sounds like a good idea, it is actually defined in StatisticalMeasures.jl here:

https://juliaai.github.io/StatisticalMeasures.jl/dev/auto_generated_list_of_measures/#StatisticalMeasures.MulticlassFScore