Fix formatting of commented guards #12721

Job	Run time
validate	13s
rustfmt	13s
lint-build	55s
test-wasm	1m 34s
test (stable, x86_64-pc-windows-msvc)	4m 54s
test (stable, aarch64-unknown-linux-gnu)	3m 8s
test (stable, x86_64-unknown-linux-musl)	6m 53s
test (stable, aarch64-unknown-linux-musl)	4m 14s
test (stable, aarch64-apple-darwin, macos-latest, arm64, cargo, true)	5m 16s
test (stable, x86_64-unknown-linux-gnu)	3m 59s
test (stable, x86_64-apple-darwin)	11m 17s
test-projects	2m 57s
	45m 33s

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