Fix **Footer** test for `version={true}` – can validly generate a no-version footer

The test for **Footer** that checks that passing booleans to the `version` prop is okay expects that the version shows up if you pass `true` (either explicitly, or implicitly via naming the prop).

Actually, if there's no `REACT_APP_VERSION` key in `process.env`, the **Footer** will validly have no version string. So that test is a bit wrong and needs fixing.