Bump redis-store to 1.6.0
This version supports SSL/TLS via the redis:// URL scheme: https://github.com/redis-store/redis-store/blob/master/CHANGELOG.md
Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/47702
This version supports SSL/TLS via the redis:// URL scheme: https://github.com/redis-store/redis-store/blob/master/CHANGELOG.md
Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/47702