Fix a semantic mistake in #[builder(derive(Into))] docs (this time for real) #859

Job	Run time
cargo-machete	3s
cargo-fmt	15s
cargo-doc (ubuntu)	19s
cargo-lock	6s
cargo-doc (windows)	1m 43s
cargo-doc (macos)	38s
cargo-miri	1m 45s
compilation-benchmarks	2m 2s
prettier	6s
taplo-fmt	3s
runtime-benchmarks (args_3)	48s
test-msrv (ubuntu)	1m 5s
runtime-benchmarks (args_5)	1m 15s
test-stable (ubuntu)	1m 15s
test-msrv (windows)	1m 46s
runtime-benchmarks (args_10_alloc)	53s
test-unstable (beta)	24s
test-stable (windows)	4m 4s
test-msrv (macos)	1m 22s
runtime-benchmarks (args_10_structs)	58s
test-unstable (nightly)	26s
test-stable (macos)	1m 29s
runtime-benchmarks (args_10)	1m 23s
runtime-benchmarks (args_20)	49s
typos	4s
version-sync	2s
website-build	28s
	25m 31s

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