Use VueApollo for Roadmap
# Summary The [Roadmap app](https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/assets/javascripts/roadmap) currently uses Epics GraphQL API to fetch list of epics and milestones to render timeline, but it still relies completely on Vuex for state management, we need to migrate it to use VueApollo instead and get rid of Vuex.
epic