scrypt: fix doctest gating (#828) #1500

Job	Run time
test (1.85.0)	21s
test (stable)	15s
build (stable, thumbv7em-none-eabi)	16s
build (stable, wasm32-unknown-unknown)	18s
build (1.85.0, wasm32-unknown-unknown)	19s
build (1.85.0, thumbv7em-none-eabi)	18s
minimal-versions / minimal-versions	27s
	2m 14s

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