Indentation of items is lost in examples in documentation with `-Zrustdoc-scrape-examples`

[WaffleLapkin]

See this screenshot:

In the example in documentation function signature is not indented, while in the source file it is indented.

cc @willcrichton

@rustbot label +A-rustdoc-scrape-examples +A-rustdoc-ui +T-rustdoc

Meta

rustc --version --verbose:

rustc 1.60.0-nightly (777bb86bc 2022-01-20)
binary: rustc
commit-hash: 777bb86bcdbc568be7cff6eeeaaf81a89b4aa50b
commit-date: 2022-01-20
host: x86_64-unknown-linux-gnu
release: 1.60.0-nightly
LLVM version: 13.0.0