chore: rm `doc_auto_cfg` #263

Job	Run time
doctest	1m 5s
feature-checks	58s
docs	1m 6s
clippy	1m 5s
fmt	14s
test stable	1m 9s
test stable --all-features	1m 10s
test stable --no-default-features	1m 12s
test nightly --no-default-features	1m 9s
test 1.88 --no-default-features	1m 7s
test nightly --all-features	1m 11s
test 1.88	1m 13s
deny / cargo deny check	18s
test nightly	1m 12s
ci-success	4s
	14m 13s

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