⚠️ Remove top-level calls to pip_install

[jcfr]

Packages should NOT be installed simply after importing the script.

Additionally, the user should be notified that their installation will be modified and offered the option to opt-out.

See https://slicer.readthedocs.io/en/latest/developer_guide/python_faq.html#can-i-use-any-python-package-in-a-slicer-module

[jcfr]

re: #59

[Jeanneclre]

Hello @jcfr

Thank you for your input.
I was looking into the best way to do it for AREG, re: #61 but I've read the doc you sent and I don't exactly understand how we have to install the package in practice. Should we add a function that is called when running our module (at the start of the process) or should it be a file such as a requirement.txt?