Leftover crates

[FintanH]

Since we're merging crates into a single crate (#114), we have left them duplicated in radicle-git for publishing purposes. However, I believe heartwood is the only dependent. At least according to crates.io there are no official dependents:

• https://crates.io/crates/git-commit/reverse_dependencies
• https://crates.io/crates/git-trailers/reverse_dependencies (only git-commit)
• https://crates.io/crates/git-ref-format/reverse_dependencies (only radicle-surf and radicle-git-ext)

I'm thinking that we just yank these from crates and delete the remnants from radicle-git.