force batch sizes of `ReshufflingBatchSubsampling` to have the same size#228

Red-Portal wants to merge 2 commits intobackport-0.6TuringLang/AdvancedVI.jl:backport-0.6from

patch_subsampling_prepTuringLang/AdvancedVI.jl:patch_subsampling_prepCopy head branch name to clipboard