Remove deprecation warning:

[schneems]

warning: `default_features` is deprecated in favor of `default-features` and will not work in the 2024 edition
(in the `tokio` dependency)
    Checking itoa v1.0.9
    Checking serde v1.0.192
   Compiling fs-err v2.11.0 (/home/runner/work/fs-err/fs-err)
    Checking ryu v1.0.15
    Checking serde_json v1.0.100

[schneems]

I'm getting an unexpected error in CI and not sure why. This PR was an attempt to diagnose it. There's still a deprecation warning in the output, but it's not related to this failure:

error: unexpected `cfg` condition name: `rustc_1_63`
  --> src/path.rs:[16](https://github.com/andrewhickman/fs-err/actions/runs/9925686637/job/27418370104#step:8:17):11
   |
16 |     #[cfg(rustc_1_63)]
   |           ^^^^^^^^^^
   |
   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `docsrs`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
   = help: consider using a Cargo feature instead
   = help: or consider adding in `Cargo.toml` the `check-cfg` lint config for the lint:
            [lints.rust]
            unexpected_cfgs = { level = "warn", check-cfg = ['cfg(rustc_1_63)'] }
   = help: or consider adding `println!("cargo::rustc-check-cfg=cfg(rustc_1_63)");` to the top of the `build.rs`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
   = note: `-D unexpected-cfgs` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(unexpected_cfgs)]`

That cfg should be emitted by autocfg which was added in my PR https://github.com/andrewhickman/fs-err/blob/25ac4217fed035c9283f8612d29305d480de40d6/build.rs but for some reason it's not working.

Notably it doesn't look like autocfg is installed in the build output:

Run actions-rs/cargo@v1
/home/runner/.cargo/bin/cargo test
 Downloading crates ...
  Downloaded itoa v1.0.[9](https://github.com/andrewhickman/fs-err/actions/runs/11391081315/job/31694081963?pr=61#step:6:10)
  Downloaded serde v1.0.192
  Downloaded ryu v1.0.15
  Downloaded serde_json v1.0.[10](https://github.com/andrewhickman/fs-err/actions/runs/11391081315/job/31694081963?pr=61#step:6:11)0
   Compiling serde v1.0.192
   Compiling serde_json v1.0.100
   Compiling ryu v1.0.15
   Compiling itoa v1.0.9
warning: unexpected `cfg` condition name: `rustc_1_63`
  --> src/path.rs:16:[11](https://github.com/andrewhickman/fs-err/actions/runs/11391081315/job/31694081963?pr=61#step:6:12)
   |
16 |     #[cfg(rustc_1_63)]
   |           ^^^^^^^^^^
   |
   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `docsrs`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
   = help: consider using a Cargo feature instead
   = help: or consider adding in `Cargo.toml` the `check-cfg` lint config for the lint:
            [lints.rust]
            unexpected_cfgs = { level = "warn", check-cfg = ['cfg(rustc_1_63)'] }
   = help: or consider adding `println!("cargo::rustc-check-cfg=cfg(rustc_1_63)");` to the top of the `build.rs`
   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
   = note: `#[warn(unexpected_cfgs)]` on by default

[schneems]

Figured it out cuviper/autocfg#70