Fix LLVM offload install docs to use semicolon-separated CMake lists

[sharesth23]

Update so the LLVM CMake example uses and , which is the correct list separator syntax for LLVM CMake options.[Docs] Remove shortcode from models page heading

[rustbot]

The rustc-dev-guide subtree was changed. If this PR only touches the dev guide consider submitting a PR directly to rust-lang/rustc-dev-guide otherwise thank you for updating the dev guide with your changes.

cc @BoxyUwU, @tshepang

[rustbot]

r? @eholk

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