Bump `crypto-bigint` to v0.7.0-rc.28 #1237

Job	Run time
build (1.85.0, wasm32-unknown-unknown)	26s
test (1.85.0)	56s
build (stable, thumbv7em-none-eabi)	21s
build (1.85.0, thumbv7em-none-eabi)	24s
build (stable, wasm32-unknown-unknown)	17s
test (stable)	50s
nightly	1m 10s
minimal-versions	-1s
	4m 23s

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