Adapt to API changes in StatsBase v0.28

Weighed mean takes `dims` keyword argument now.

Author: oschulz

src/statsbase_support.jl

@@ -4,7 +4,7 @@
 Base.sum(X::AbstractVectorOfSimilarArrays{T,M}, w::StatsBase.AbstractWeights) where {T,M} = sum(flatview(X), w, M + 1)
 
 Statistics.mean(X::AbstractVectorOfSimilarArrays{T,M}, w::StatsBase.AbstractWeights) where {T,M} =
-    mean(flatview(X), w, M + 1)
+    mean(flatview(X), w, dims = M + 1)
 
 Statistics.var(X::AbstractVectorOfSimilarArrays{T,M}, w::StatsBase.AbstractWeights; corrected::Bool = true) where {T,M} =
     var(flatview(X), w, M + 1; corrected = corrected)