Bump actions/checkout from 5 to 6 #329

Job	Run time
miri (s390x-unknown-linux-gnu)	1m 2s
test (1.85.0)	37s
rustfmt	9s
test (stable)	33s
miri (x86_64-unknown-linux-gnu)	40s
careful	1m 3s
build (1.85.0, thumbv7em-none-eabi)	17s
doc	14s
build (1.85.0, armv7a-none-eabi)	32s
build (stable, armv7a-none-eabi)	32s
clippy	17s
build (stable, wasm32-unknown-unknown)	31s
build (1.85.0, wasm32-unknown-unknown)	21s
build (stable, thumbv7em-none-eabi)	10s
build (1.85.0, armv7a-none-eabi)	50s
build (1.85.0, thumbv7em-none-eabi)	52s
build (stable, armv7a-none-eabi)	48s
build (1.85.0, wasm32-unknown-unknown)	51s
build (stable, wasm32-unknown-unknown)	47s
build (stable, thumbv7em-none-eabi)	51s
miri (x86_64-unknown-linux-gnu)	40s
doc	14s
miri (s390x-unknown-linux-gnu)	1m 2s
clippy	17s
rustfmt	9s
test (1.85.0)	37s
test (stable)	33s
careful	1m 3s
	16m 32s

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