Replace deprecated yield_fixture with fixture

Committed via https://github.com/asottile/all-repos
diff --git a/tests/conftest.py b/tests/conftest.py
index 87fec70..da206cb 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -7,7 +7,7 @@
 from pre_commit_hooks.util import cmd_output
 
 
-@pytest.yield_fixture
+@pytest.fixture
 def temp_git_dir(tmpdir):
     git_dir = tmpdir.join('gits')
     cmd_output('git', 'init', '--', git_dir.strpath)