docs.rs failing to build recently published crates

[heaths]

Because of rust-lang/rust#138907, docs.rs is failing to document our crates published 2025-10-03:

docs.rs failed to build azure_core-0.29.0
Please check the build logs for more information.
See Builds for ideas on how to fix a failed build, or Metadata for how to configure docs.rs builds.
If you believe this is docs.rs' fault, open an issue.

From https://docs.rs/crate/azure_core/0.29.0/builds/2555808:

[INFO] [stderr]  Documenting azure_core v0.29.0 (/opt/rustwide/workdir)
[INFO] [stderr] error[E0557]: feature has been removed
[INFO] [stderr]  --> src/lib.rs:7:29
[INFO] [stderr]   |
[INFO] [stderr] 7 | #![cfg_attr(docsrs, feature(doc_auto_cfg))]
[INFO] [stderr]   |                             ^^^^^^^^^^^^ feature has been removed
[INFO] [stderr]   |
[INFO] [stderr]   = note: removed in CURRENT_RUSTC_VERSION; see <https://github.com/rust-lang/rust/pull/138907> for more information
[INFO] [stderr]   = note: merged into `doc_cfg`
[INFO] [stderr] 
[INFO] [stderr] error: Compilation failed, aborting rustdoc

Long term, we'll hopefully be able to remove or somehow replace cfg_attr(docsrs, ...). See tracking issue #2366 for that. We also should put cargo-docs-rs back into the PR and/or CI pipelines: #3117