replace yield_fixture decorator by fixture
replace yield_fixture decorator by fixture

https://docs.pytest.org/en/latest/yieldfixture.html

> Since pytest-3.0, fixtures using the normal fixture decorator can use a yield statement to provide fixture values and execute teardown code, exactly like yield_fixture in previous versions.
> 
> Marking functions as yield_fixture is still supported, but deprecated and should not be used in new code.
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