kem

signature: remove `derive` feature #1508

Job	Run time
test (1.85.0)	19s
build (1.85.0, thumbv7em-none-eabi)	20s
test (stable)	21s
build (1.85.0, wasm32-unknown-unknown)	17s
build (stable, wasm32-unknown-unknown)	13s
build (stable, thumbv7em-none-eabi)	17s
	1m 47s

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