Mark test_utils as a verification test.

Without this it won't run when verification-tests.yml workflow executes with
"pytest -m verification".

See `pytest` docs [Specifying which tests to
run](https://docs.pytest.org/en/stable/how-to/usage.html#specifying-which-tests-to-run)
and [Working with custom
markers](https://docs.pytest.org/en/7.1.x/example/markers.html).

tests/verification/test_utils.py

@@ -5,7 +5,7 @@
 from .utils import assert_public_method_signature_equality
 
 
-pytestmark = [pytest.mark.disable_db]
+pytestmark = [pytest.mark.verification, pytest.mark.disable_db]
 
 
 class TestPublicMethodSignatureEquality: