hmac

hmac: bump `digest` to v0.11.0-pre.8 (#156) #288

Job	Run time
build (1.72.0, thumbv7em-none-eabi)	19s
build (1.72.0, wasm32-unknown-unknown)	21s
build (stable, thumbv7em-none-eabi)	7s
test (1.72.0)	21s
build (stable, wasm32-unknown-unknown)	17s
test (stable)	17s
minimal-versions / minimal-versions	27s
	2m 9s

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