Bump actions/download-artifact from 2 to 3 #269

Job	Run time
miri	1m 26s
build (ubuntu, stable, locked, true)	12m 18s
build (windows, stable, locked, false)	24m 5s
no_std	33s
build (macos, stable, locked, false)	34m 42s
build (ubuntu, nightly, locked, false)	19m 16s
build (ubuntu, beta, locked, false)	12m 19s
build (ubuntu, stable, latest, false)	11m 59s
build (ubuntu, stable, minimal, false)	12m 4s
features	24m 28s
fuzz	14m 12s
deploy	0s
	2h 47m 22s

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