block-padding+inout: remove `std` feature #1740

Job	Run time
test (1.81.0)	17s
build (1.81.0, thumbv7em-none-eabi)	17s
test (stable)	15s
build (1.81.0, wasm32-unknown-unknown)	14s
build (stable, thumbv7em-none-eabi)	48s
build (stable, wasm32-unknown-unknown)	17s
minimal-versions / minimal-versions	27s
	2m 35s

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