Switch to pytest-notebook for notebook testing

[astrofle]

pytest-notebook is a better option for notebook testing. It makes sure that the outputs remain the same. However, this same also means we have to write up the rules so that paths and other system dependent outputs are not tested. This can be configured using: https://pytest-notebook.readthedocs.io/en/latest/user_guide/tutorial_config.html#regex-pattern-replacement