Unmaintained scripts in `pisa_tests` directory

[thehrh]

• https://github.com/icecube/pisa/blob/master/pisa_tests/test_changes_with_combined_pidreco.py uses nonexistent pipeline configs to address pisa 2 vs. 3 compatibility issues
• https://github.com/icecube/pisa/blob/master/pisa_tests/test_command_lines.sh tries to run a nonexistent python script (pisa/scripts/make_toy_events.py) and assumes every .py file to have a command-line test set up
• https://github.com/icecube/pisa/blob/master/pisa_tests/test_hypo_testing.sh tries to run two nonexistent scripts
• https://github.com/icecube/pisa/blob/master/pisa_tests/likelihoods_1D_test.py is an unwieldy thing that imports seaborn and that looks like something that should be placed with other studies in the fridge (it doesn't exactly explain what it intends to demonstrate or why it should be shipped with pisa)