cms: remove `pem` feature (#1563) #2465

Job	Run time
build (1.70.0, wasm32-unknown-unknown)	25s
build (1.70.0, thumbv7em-none-eabi)	29s
test (i686-unknown-linux-gnu, 1.70.0, sudo apt update && sudo apt install gcc-multilib)	4m 31s
build (stable, wasm32-unknown-unknown)	19s
test (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	4m 2s
build (stable, thumbv7em-none-eabi)	24s
test (x86_64-unknown-linux-gnu, 1.70.0)	4m 14s
test (x86_64-unknown-linux-gnu, stable)	3m 45s
minimal-versions / minimal-versions	2m 27s
	20m 36s

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