Fix deprecated constant in docs example #2712

Job	Run time
docs	17s
check-cfg	22s
minimal	12s
msrv	50s
quickchecking	24s
rustfmt-clippy	26s
test-book	7s
test-expectations (ubuntu-latest)	36s
test-no-headers	26s
test-expectations (macos-latest)	39s
test (ubuntu-latest, 9.0, 0, 0, 0, 0)	1m 55s
test (ubuntu-latest, 9.0, 0, 0, 1, 0)	1m 37s
test (ubuntu-latest, 9.0, 0, 1, 0, 0)	1m 37s
test (ubuntu-latest, 9.0, 0, 1, 1, 0)	1m 33s
test (ubuntu-latest, 9.0, 1, 0, 0, 0)	2m 14s
test (ubuntu-latest, 9.0, 1, 0, 1, 0)	2m 42s
test (ubuntu-latest, 9.0, 1, 1, 0, 0)	2m 8s
test (ubuntu-latest, 9.0, 1, 1, 1, 0)	2m 6s
test (ubuntu-latest, 16.0, 0, 0, 0, 0)	4m 9s
test (ubuntu-latest, 16.0, 0, 0, 1, 0)	4m 1s
test (ubuntu-latest, 16.0, 0, 1, 0, 0)	3m 54s
test (ubuntu-latest, 16.0, 0, 1, 1, 0)	4m 16s
test (ubuntu-latest, 16.0, 1, 0, 0, 0)	4m 35s
test (ubuntu-latest, 16.0, 1, 0, 1, 0)	4m 45s
test (ubuntu-latest, 16.0, 1, 1, 0, 0)	4m 50s
test (ubuntu-latest, 16.0, 1, 1, 1, 0)	4m 51s
test (ubuntu-latest, 16.0, 0, 0, 1)	2m 40s
test (macos-latest, 16.0, 0, 0, 0)	1m 55s
success	1s
	1h 0m 8s

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