cli: Print the identity parent in `cob show`

The parent that points to the identity document commit was missing
from the output.

radicle-cli/src/commands/cob.rs

@@ -116,6 +116,7 @@ pub fn run(options: Options, ctx: impl term::Context) -> anyhow::Result<()> {
                 .to_rfc2822();
 
                 term::print(term::format::yellow(format!("commit {}", op.id)));
+                term::print(term::format::tertiary(format!("parent {}", op.identity)));
                 for parent in op.parents {
                     term::print(format!("parent {}", parent));
                 }