Fix assertion in `TestCheckParseValues::test_warns_bad_type` #699

Job	Run time
simple-checks	11s
unit-tests (py3mypy, tox.ini)	36s
unit-tests (py3, tox.ini)	39s
integration-tests (py3-generic, tox-integration.ini)	1m 54s
integration-tests (py3-mqtt, tox-integration.ini)	4m 17s
integration-tests (py3-hooks, tox-integration.ini)	1m 23s
integration-tests (py3-advanced, tox-integration.ini)	1m 27s
	10m 27s

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