Bump `rand` to v0.10.0-rc.8 #3431

Job	Run time
test (1.85.0)	21s
build (1.85.0, wasm32-unknown-unknown)	17s
minimal-versions / minimal-versions	27s
build (stable, thumbv7em-none-eabi)	18s
build (stable, wasm32-unknown-unknown)	24s
test (stable)	21s
build (1.85.0, thumbv7em-none-eabi)	21s
	2m 29s

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