We add 2 refactors:

1. Add `attr_reader :user` to RecentItems because this will be used by
`RecentEpics` since the `EpicsFinder` cannot search outside of a single
group like the `IssuesFinder` does so we need to override `#search`
instead
2. Apply the limit=5 in the RecentItems module instead of the
SearchHelper caller. This is necessary for when we implement Epics
search because we'll need to do a permissions check on the limited items
before returning them