Remove preserve_order in serde_json #2422

Job	Run time
test stable --no-default-features	1m 13s
test no_std	27s
test stable	1m 3s
test stable --all-features	1m 13s
test beta --no-default-features	2m 4s
check no-default-features	21s
test beta	1m 57s
test beta --all-features	2m 0s
check serde	20s
test nightly --no-default-features	2m 7s
check std	18s
test nightly	2m 2s
test nightly --all-features	2m 11s
clippy	1m 18s
docs	1m 12s
fmt	12s
	19m 58s

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