Currently it is not possible to insert lines over connected lines

[christianbrugger]

Fix following testcase:

https://github.com/LogikSim/LogikSim/blob/00d180f3/src/tests/test_inserting.py#L308-L326

[hacst]

BTW: Imho instead of skipping the test it's better to mark it as expected to fail. That means it will still run during testing.