cms: remove `pem` feature (#1563) #1430

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	1m 5s
test (1.65.0)	1m 33s
build (1.65.0, wasm32-unknown-unknown)	1m 6s
test (stable)	22s
build (stable, thumbv7em-none-eabi)	14s
build (stable, wasm32-unknown-unknown)	12s
minimal-versions / minimal-versions	33s
	5m 5s

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