sha3: bump `keccak` dependency to v0.2.0-pre.0 #296

Job	Run time
minimal-versions / minimal-versions	29s
set-msrv / set-msrv	3s
test (1.71.0)	39s
build (1.71.0, thumbv7em-none-eabi)	21s
test (stable)	29s
build (1.71.0, wasm32-unknown-unknown)	20s
build (stable, thumbv7em-none-eabi)	12s
build (stable, wasm32-unknown-unknown)	19s
	2m 52s

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