Fix LSP violations in test files

[cdce8p]

Extracted from #18356

[cdce8p]

#18356 changed the superclass implementation instead. However as this is the only violation, I'm not sure that's necessary here.

mypy/mypy/test/data.py

Lines 818 to 820 in d79d89e

	@abstractmethod
	def run_case(self, testcase: DataDrivenTestCase) -> None:
	raise NotImplementedError