tokio recipe is still using a git dependency and the old method syntax

Need to be updated: https://godot-rust.github.io/book/gdnative/recipes/async-tokio.html

Related PR: https://github.com/godot-rust/gdnative/pull/975, released to crates in [`0.11.1`](https://github.com/godot-rust/gdnative/releases/tag/0.11.1)