chore: update GitHub Actions to Node 20 (#1338) #849

Job	Run time
check no-default-features	15s
check serde	19s
check std	17s
test no_std	23s
test stable --no-default-features	47s
test stable	55s
clippy	1m 10s
test stable --all-features	1m 17s
test beta --no-default-features	2m 19s
test beta	2m 15s
docs	1m 10s
test beta --all-features	2m 30s
test nightly --no-default-features	2m 20s
fmt	5s
test nightly	2m 16s
test nightly --all-features	2m 29s
	20m 47s

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