cms: remove `pem` feature (#1563) #2498

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	1m 9s
test (1.65.0)	1m 32s
build (1.65.0, wasm32-unknown-unknown)	1m 6s
test (stable)	32s
build (stable, thumbv7em-none-eabi)	10s
build (stable, wasm32-unknown-unknown)	12s
minimal-versions / minimal-versions	32s
	5m 13s

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