.pylintrc: Simplify config, only list overrides

Rather than having the full .pylintrc, only list the overrides that we have compared to the default options. This makes it easy to identify what options we have modified, which is also similar to what we do for configuring other tools.

At the same time, also remove overrides corresponding to the gi module. They were added when this repository depended on the ostree module but that's no longer the case.