cgdb: update style

The `skip_clean 'share/info'` in here is no longer needed, as we no longer strip info directories.

However, `info cgdb` shows me the manpage, which says to use `info CGDB` to get the documentation. If I type that with uppercase, no documentation node is found.

So something is going on with the documentation here, but I haven't tracked it to see if it is an upstream issue, or an issue with Homebrew removing certain "info dir" directories.