tests: switch to using pip (as a module) in test-version-install.t Let's switch to using pip to install the extensions to avoid a SetuptoolsDeprecationWarning about running setup.py directly. This also avoids the warning about python_requires apparently. The "running as root" warning cannot be simply avoided by using a different CI image. We do have v2.1 images that default to ci-runner user, but no one forbids people from running the test locally as a root user, one way or another. Running pip as root shouldn't matter in this case, since it's not a real system install, so this particular warning is always irrelevant.