[FIX] py_elephant fix tests

• This merge request addresses the issue of tests failing due to the way test data is created in some tests.
• The core functionality of Elephant is unaffected and works correctly with Neo versions 0.13.1 and higher.
• The problem is isolated to the lazy creation of test data, which will be properly handled in Elephant 1.2.0, see: https://github.com/NeuralEnsemble/elephant/pull/634

Suggested Solution: For now, the tests that are affected by this test data creation issue are skipped. Since the actual functionality remains intact, skipping the tests allows us to proceed without blocking !555 (merged) and !583 (merged) .