docs: The data-layout field is no longer required in custom targets

[phil-opp]

The data-layout field is no longer required. It was made optional in 958d563.

The os field is always required.

Related to #31367

[rust-highfive]

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

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[japaric]

Could you change 'data-layout' for 'os'? That one is also a required field.

[phil-opp]

Done. It seems like the list of required items is complete now.

[japaric]

Done. It seems like the list of required items is complete now.

Yes, thank you!

@bors: r+ rollup

[bors]

📌 Commit 9532602 has been approved by japaric

[bors]

⌛ Testing commit 9532602 with merge 978bc07...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-64-x-armhf, auto-linux-64-x-armsf, auto-linux-64-x-freebsd, auto-linux-64-x-netbsd, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild