Removes `cmd.Version()`.
Removes `cmd.Version()`.

The `Version()` function is a less useful alternative to
`VersionString()` and isn't necessary. It used a fixed "0.1.0" prefix
that doesn't match a release tag, it also doesn't print Go & host
information that `VersionString()` does.

Less code = less bugs!

ibukanov/boulder,jfrazelle/boulder,lucasallan/boulder,sophie-h/boulder,jcjones/boulder,jsha/boulder,jfrazelle/boulder,ibukanov/boulder,bmw/boulder,jfrazelle/boulder,jcjones/boulder,ZCloud-Firstserver/boulder,jfrazelle/boulder,jsha/boulder,letsencrypt/boulder,bmw/boulder,lucasallan/boulder,ZCloud-Firstserver/boulder,ZCloud-Firstserver/boulder,letsencrypt/boulder,jsha/boulder,jcjones/boulder,lucasallan/boulder,bmw/boulder,jcjones/boulder,ZCloud-Firstserver/boulder,letsencrypt/boulder,sophie-h/boulder,sophie-h/boulder,ibukanov/boulder