RELNOTES: ps(1): Document change in behavior for '-a'/'-A'

[olce]

Summary

While here, mention a possible practical issue with '-J', as reported by
dch@. This option was introduced by commit "Add -J to filter by
matching jail IDs and names." (13767130c7147ae7182a, r265229), which
unfortunately talked about '-J' being a filter while actually
implementing it as a regular selection option which adds to the
processes to display.