Apply suggestions from code review

Co-authored-by: Zac Hatfield-Dodds <zac.hatfield.dodds@gmail.com>

testing/deprecated_test.py

@@ -284,7 +284,7 @@ def test_importing_instance_is_deprecated(pytester: Pytester) -> None:
 def test_fixture_disallow_on_marked_functions():
     """Test that applying @pytest.fixture to a marked function warns (#3364)."""
     with pytest.warns(
-        pytest.PytestDeprecationWarning,
+        pytest.PytestRemovedIn8Warning,
         match=r"Marks applied to fixtures have no effect",
     ) as record:
 
@@ -303,7 +303,7 @@ def test_fixture_disallow_on_marked_functions():
 def test_fixture_disallow_marks_on_fixtures():
     """Test that applying a mark to a fixture warns (#3364)."""
     with pytest.warns(
-        pytest.PytestDeprecationWarning,
+        pytest.PytestRemovedIn8Warning,
         match=r"Marks applied to fixtures have no effect",
     ) as record:
 
@@ -319,7 +319,7 @@ def test_fixture_disallow_marks_on_fixtures():
 def test_fixture_disallowed_between_marks():
     """Test that applying a mark to a fixture warns (#3364)."""
     with pytest.warns(
-        pytest.PytestDeprecationWarning,
+        pytest.PytestRemovedIn8Warning,
         match=r"Marks applied to fixtures have no effect",
     ) as record: