CI: fix `sha2` build (#623) #660

Job	Run time
minimal-versions / minimal-versions	34s
set-msrv / set-msrv	3s
test (1.71.0)	40s
build (1.71.0, thumbv7em-none-eabi)	19s
test (stable)	31s
build (1.71.0, wasm32-unknown-unknown)	19s
build (stable, thumbv7em-none-eabi)	23s
build (stable, wasm32-unknown-unknown)	20s
	3m 9s

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