Replace deprecated yield_fixture with fixture

Committed via https://github.com/asottile/all-repos
diff --git a/tests/check_merge_conflict_test.py b/tests/check_merge_conflict_test.py
index a999aca..8a848ba 100644
--- a/tests/check_merge_conflict_test.py
+++ b/tests/check_merge_conflict_test.py
@@ -12,7 +12,7 @@
 from testing.util import write_file
 
 
-@pytest.yield_fixture
+@pytest.fixture
 def f1_is_a_conflict_file(tmpdir):
     # Make a merge conflict
     repo1 = tmpdir.join('repo1')
@@ -67,7 +67,7 @@
         yield
 
 
-@pytest.yield_fixture
+@pytest.fixture
 def repository_is_pending_merge(tmpdir):
     # Make a (non-conflicting) merge
     repo1 = tmpdir.join('repo1')