Add rubocop linting for misplacement of ee only classes

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/165869



Merged-by: Allison Browne <abrowne@gitlab.com>
Approved-by: Allison Browne <abrowne@gitlab.com>
Reviewed-by: Doug Stull <dstull@gitlab.com>
Co-authored-by: Doug Stull <dstull@gitlab.com>