Improve os::linux documentation (#29367)

[ctjhoa]

Improve os::linux documentation according to #29367

r? @steveklabnik

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @steveklabnik (or someone else) soon.

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[steveklabnik]

Wonderful, thanks! I have one tiny nit and then we can merge.

[steveklabnik]

can you add a /// above this line? With markdown, just one \n doesn't actually cause a line break; it will bleed together as one paragraph. We try to usually have a short summary, a blank space, and then elaborate more 😄

[ctjhoa]

@steveklabnik done

[steveklabnik]

@bors: r+ rollup

awesome, thanks!

[bors]

📌 Commit 732fe24 has been approved by steveklabnik

[frewsxcv]

@bors r-

Looks like there's a tidy error:

/checkout/src/libstd/os/linux/fs.rs:60: line longer than 100 chars

[ctjhoa]

@frewsxcv @steveklabnik this should be ok.

[steveklabnik]

@bors: r+ rollup

👍

[bors]

📌 Commit b36cff5 has been approved by steveklabnik