`gem build` warned that an open-ended `>= 4.0` constraint lets
ViewComponent 5.0 install for consumers automatically — even though
we've only tested against 4.x. The SemVer-aware convention is
`~> 4.0`, which expands to `>= 4.0, < 5.0`. If ViewComponent 5 ships
and is compatible, we can loosen this in a follow-up release.