Relax dependency criteria

[danobi]

Before, we were pinning dependencies down to the patch version. This prevents us from picking up bug fixes. It also (I think) caused failures like this:

$ cargo install vmtest
    Updating crates.io index
  Installing vmtest v0.12.0
error: failed to compile `vmtest v0.12.0`, intermediate artifacts can be found at `/tmp/cargo-installmaJQZ0`

Caused by:
  failed to select a version for the requirement `clap = "^4.0.26"`
  candidate versions found which didn't match: 3.2.25, 3.2.24, 3.2.23, ...
  location searched: crates.io index
  required by package `vmtest v0.12.0`