Update git2 requirement from 0.7 to 0.8
Update git2 requirement from 0.7 to 0.8

Updates the requirements on [git2](https://github.com/alexcrichton/git2-rs) to permit the latest version.
- [Release notes](https://github.com/alexcrichton/git2-rs/releases)
- [Commits](https://github.com/alexcrichton/git2-rs/compare/0.7.0...git2-curl-0.8.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
TomasTomecek/pretty-git-prompt,TomasTomecek/pretty-git-prompt,TomasTomecek/pretty-git-prompt