Bump actions/checkout from 4 to 6 #68

Job	Run time
check-assets	7s
build (windows, 386)	53s
build (openbsd, amd64)	52s
build (windows, amd64)	52s
build (freebsd, amd64)	52s
build (freebsd, 386)	1m 1s
build (openbsd, 386)	53s
build (linux, 386)	48s
build (linux, amd64)	48s
build (linux, arm, 5)	56s
build (darwin, arm64)	50s
build (android, amd64, android-amd64)	1m 21s
build (darwin, amd64)	54s
build (linux, arm, 6)	55s
build (linux, mips64)	54s
build (linux, riscv64)	53s
build (windows, arm64)	54s
build (linux, mips)	1m 19s
build (linux, mipsle)	1m 25s
build (linux, loong64)	55s
build (freebsd, arm64)	55s
build (android, arm64)	1m 17s
build (linux, arm, 7)	56s
build (linux, ppc64)	51s
build (linux, ppc64le)	54s
build (freebsd, arm, 7)	50s
build (linux, s390x)	55s
build (openbsd, arm64)	55s
build (linux, mips64le)	53s
build (openbsd, arm, 7)	59s
build (linux, arm64)	55s
build (windows, arm, 7)	53s
	29m 35s

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