docstore/memdocstore: apply limit after sorting (#2978)
docstore/memdocstore: apply limit after sorting (#2978)

Fixes google/go-cloud#2977

Co-authored-by: Robert van Gent <433303f4179d1c7cc6a6475763ba041ad4a36134@google.com>
google/go-cloud,google/go-cloud,google/go-cloud