dsa: bump `crypto-bigint` to v0.7 final release (#1247) #1502

Job	Run time
build (thumbv7em-none-eabi, stable)	19s
build (thumbv7em-none-eabi, 1.85.0)	16s
test (stable)	19s
build (wasm32-unknown-unknown, 1.85.0)	18s
test (1.85.0)	20s
build (wasm32-unknown-unknown, stable)	22s
	1m 54s

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