cms: remove `pem` feature (#1563) #2583

Job	Run time
build (1.81.0, thumbv7em-none-eabi)	20s
test (1.81.0)	18s
build (1.81.0, wasm32-unknown-unknown)	17s
test (stable)	12s
build (stable, thumbv7em-none-eabi)	20s
build (stable, wasm32-unknown-unknown)	11s
minimal-versions / minimal-versions	32s
	2m 10s

Provide feedback