"Rustdocs are clean (amd64, nightly)" CI check is failing

[Jefffrey]

Describe the bug

CI failing on unrelated PRs: https://github.com/apache/arrow-rs/actions/runs/8956610392/job/24627590071?pr=5679

    Checking parquet v51.0.0 (/__w/arrow-rs/arrow-rs/parquet)
warning: unexpected `cfg` condition name: `rustfmt`
 --> parquet/src/format.rs:8:13
  |
8 | #![cfg_attr(rustfmt, rustfmt_skip)]
  |             ^^^^^^^
  |
  = help: expected names are: `clippy`, `debug_assertions`, `doc`, `docsrs`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
  = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(rustfmt)");` to the top of the `build.rs`
  = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
  = note: `#[warn(unexpected_cfgs)]` on by default

    Checking tracing-log v0.2.0
    Checking tonic v0.11.0
    Checking arrow v51.0.0 (/__w/arrow-rs/arrow-rs/arrow)
 Documenting parquet v51.0.0 (/__w/arrow-rs/arrow-rs/parquet)
    Checking hex v0.4.3
error: unexpected `cfg` condition name: `rustfmt`
 --> parquet/src/format.rs:8:13
  |
8 | #![cfg_attr(rustfmt, rustfmt_skip)]
  |             ^^^^^^^
  |
  = help: expected names are: `clippy`, `debug_assertions`, `doc`, `docsrs`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
  = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(rustfmt)");` to the top of the `build.rs`
  = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
  = note: `-D unexpected-cfgs` implied by `-D warnings`
  = help: to override `-D warnings` add `#[allow(unexpected_cfgs)]`

error: could not document `parquet`
warning: build failed, waiting for other jobs to finish...
warning: `parquet` (lib) generated 1 warning

To Reproduce

Run CI

Expected behavior

CI succeeds for this check

Additional context

Related issue: rust-lang/rust#124735

[alamb]

Thanks you for filing this @Jefffrey

[alamb]

Proposed PR to fix: #5727

[tustvold]

label_issue.py automatically added labels {'parquet'} from #5727

[tustvold]

label_issue.py automatically added labels {'arrow'} from #5727