Fix warning about default_features being deprecated

When `cargo check` is run on master, the following warning is logged: ``` warning: `default_features` is deprecated in favor of `default-features` and will not work in the 2024 edition (in the `futures-core` dependency) warning: `default_features` is deprecated in favor of `default-features` and will not work in the 2024 edition (in the `futures-sink` dependency) ``` This does not cause the process to exit with a non-zero exit code, which means this would not have been effecting CI. This PR fixes that warning.