Enabling "glob" feature makes compilation fail on stable

[aldanor]

error[E0658]: `#[doc(cfg)]` is experimental
   --> .../include_dir-0.7.1/src/lib.rs:102:1
    |
102 | #[doc(cfg(feature = "glob"))]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I don't think you need it at all because since recently #[cfg] implies #[doc(cfg)] (https://github.com/rust-lang/rust/pull/89596).

Also, in some very rare cases when it may not work and you need to do it manually, you can do this:

• In Cargo.toml:

  [package.metadata.docs.rs]
  features = ["foo", "bar"]
  rustdoc-args = ["--cfg", "docsrs"]

• In lib.rs:

  #![cfg_attr(docsrs, feature(doc_cfg))]

• And then you can safely do:

  #[cfg_attr(docrs, doc(cfg(feature = "foo")))]

• And in order to build docs locally:

  RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --features foo,bar

[repi]

we ran into this today also when trying to upgrade to the new 0.7.1 version, blocking the upgrade