Update md5 requirement from 0.6 to 0.7
Update md5 requirement from 0.6 to 0.7

Updates the requirements on [md5](https://github.com/stainless-steel/md5) to permit the latest version.
- [Release notes](https://github.com/stainless-steel/md5/releases)
- [Commits](https://github.com/stainless-steel/md5/commits)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
rust-lang-nursery/uuid,rust-lang/uuid