Update test_apt_interface to use pytest parametrization

[laurenmarietta]

Shannon recently taught me how to parametrize tests with pytest, where you can pass the same test a list of different parameters to be run. I think the test_complete_input_generation() test in test_apt_interface.py could benefit from being parametrized. Then each individual APT/instrument combination would be run as an independent test, which I think might make debugging easier.

If there are no concerns, I would be happy to implement this myself - should be quick!