sha3: bump `keccak` dependency to v0.2.0-pre.0 #548

Job	Run time
minimal-versions / minimal-versions	36s
set-msrv / set-msrv	8s
test (1.71.0)	46s
build (1.71.0, thumbv7em-none-eabi)	27s
test (stable)	38s
build (1.71.0, wasm32-unknown-unknown)	23s
build (stable, thumbv7em-none-eabi)	26s
build (stable, wasm32-unknown-unknown)	21s
	3m 45s

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