Fix typo in example documentation #854

Job	Run time
build_python_27 (ubuntu-20.04, yes)	2m 24s
mypy	24s
build_python_27 (ubuntu-20.04, no)	2m 29s
build (3.5, yes, ubuntu-20.04)	2m 22s
build_python_27 (windows-latest, yes)	3m 54s
build (3.5, no, ubuntu-20.04)	2m 22s
test_c_windows (x64)	1m 21s
build_python_27 (windows-latest, no)	3m 50s
build (3.6, yes, ubuntu-20.04)	2m 27s
test_c_linux (0, x64)	54s
test_c_windows (win32)	1m 16s
build (3.6, no, ubuntu-20.04)	2m 18s
test_c_linux (0, x32)	1m 14s
build (3.7, yes, ubuntu-20.04)	2m 20s
test_c_linux (1, x64)	1m 16s
build (3.7, no, ubuntu-20.04)	2m 18s
test_c_linux (1, x32)	1m 3s
build (3.8, yes, ubuntu-20.04)	2m 9s
build (3.8, no, ubuntu-20.04)	2m 9s
build (3.9, yes, ubuntu-20.04)	2m 8s
build (3.9, no, ubuntu-20.04)	2m 11s
build (3.10, yes, ubuntu-20.04)	2m 8s
build (3.10, no, ubuntu-20.04)	2m 12s
build (3.11, yes, ubuntu-20.04)	1m 58s
build (3.11, no, ubuntu-20.04)	1m 53s
build (3.12-dev, yes, ubuntu-20.04)	2m 2s
build (3.12-dev, no, ubuntu-20.04)	2m 1s
build (3.11, yes, macos-12)	2m 39s
build (3.11, no, windows-latest)	4m 9s
build (3.11, yes, windows-latest)	4m 5s
build (3.12-dev, no, windows-latest)	4m 20s
build (3.12-dev, yes, windows-latest)	4m 2s
build (pypy2.7, no, ubuntu-latest)	1m 26s
build (pypy3.9, no, ubuntu-latest)	1m 43s
	1h 17m 27s

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