cargo.crates_github doesn't work anymore in the cargo_fetch PG

[Vadym-Valdis Yudaiev]

Hi,

Looks like after some changes `cargo.crates_github` broke. The @harens thought the `cargo._old_macos_compatibility` option was to blame. I do think it broke even earlier.

https://github.com/macports/macports-ports/pull/13909#issuecomment-1059773013

Anyway, for the `joshuto` port, I need cargo crate from Github, which I can't get anymore. For now, I've created a draft PR and will be waiting for a fix in PG to continue.

https://github.com/macports/macports-ports/pull/14865

- Vadym-Valdis Yudaiev