Remove the use of setuptools installation

[remyroy]

Using python setup.py install with setuptools is deprecated. It should be removed and replaced with something else. This might give us the opportunity to remove the setuptools dependency entirely. See https://pip.pypa.io/en/stable/topics/secure-installs/#do-not-use-setuptools-directly

This can be found at least in https://github.com/eth-educators/ethstaker-deposit-cli/blob/main/deposit.sh#L8

[remyroy]

Setuptools is not needed since we are not distributing this as a Python package.