Fix assertion in TestCheckParseValues::test_warns_bad_type

Fix the assertion in TestCheckParseValues::test_warns_bad_type
to use `.assert_called_with()` rather than non-existing `.called_with()`
method.  The latter is wrongly interpreted as calling a mocked method
in Python < 3.12, and therefore does not test anything at all.  Starting
with Python 3.12, it results in an error:

    AttributeError: 'called_with' is not a valid assertion. Use a spec for the mock if 'called_with' is meant to be an attribute.

Fixing the call also revealed that the assertion was incorrect, so I've
updated it to match the current call.

tests/unit/test_helpers.py

@@ -300,10 +300,10 @@ def test_warns_bad_type(self, item):
         with patch("tavern._core.dict_util.logger.warning") as wmock:
             _check_and_format_values("{fd}", {"fd": item})
 
-        assert wmock.called_with(
-            "Formatting 'fd' will result in it being coerced to a string (it is a {})".format(
-                type(item)
-            )
+        wmock.assert_called_with(
+            "Formatting '%s' will result in it being coerced to a string (it is a %s)",
+            "fd",
+            type(item),
         )
 
     @pytest.mark.parametrize("item", [1, "a", 1.3, format_keys("{s}", {"s": 2})])