intra doc links to std::env render incorrectly by including module@ disambiguator

[lopopolo]

I tried this code at the suggestion of the compiler to disanbiguate between the std::env module and std::env! macro:

//! - **core-env-system** - Activates the [`module@std::env`] backend for the
//!   [`ENV` object][core-obj-env]. When this feature is disabled, access to the
//!   environ is emulated with an in-memory store.

I expected to see this happen: a rendered docstring like:

core-env-system - Activates the std::env backend for the ENV object. When this feature is disabled, access to the environ is emulated with an in-memory store.

Instead, this happened: The module disambiguator was included in the rendered docs:

core-env-system - Activates the module@std::env backend for the ENV object. When this feature is disabled, access to the environ is emulated with an in-memory store.

Meta

$ cargo +nightly --version
cargo 1.47.0-nightly (ab32ee88d 2020-08-10)
[06:56] [~/dev/artichoke/artichoke]
$ rustc +nightly -Vv
rustc 1.47.0-nightly (30f0a0768 2020-08-18)
binary: rustc
commit-hash: 30f0a07684f6c1f5df62d69e9519d82e13d6bf2d
commit-date: 2020-08-18
host: x86_64-apple-darwin
release: 1.47.0-nightly
LLVM version: 10.0
[06:56] [~/dev/artichoke/artichoke]
$ rustdoc +nightly -Vv
rustdoc 1.47.0-nightly (30f0a0768 2020-08-18)
binary: rustdoc
commit-hash: 30f0a07684f6c1f5df62d69e9519d82e13d6bf2d
commit-date: 2020-08-18
host: x86_64-apple-darwin
release: 1.47.0-nightly
LLVM version: 10.0

[lopopolo]

A workaround is to write the doc string like this:

//! - **core-env-system** - Activates the [`std::env`](module@std::env) backend
//!   for the [`ENV` object][core-obj-env]. When this feature is disabled,
//!   access to the environ is emulated with an in-memory store.

[jyn514]

Duplicate of #65354