info: move `accumulate` to deprecated exercises (#497)
info: move `accumulate` to deprecated exercises (#497)

With this commit, `configlet info` no longer includes the `accumulate`
exercise in the list of exercises that a track could implement from the
`exercism/problem-specifications` repo.

Upstream:
https://github.com/exercism/problem-specifications/commit/574c14b34021

exercism/configlet