setup.py: don't require 'gi'

Turns out this is not the gi.repository but a different package:
    'Command line to private gist.  Example: gi.py myFile'

It's incompatible with python3 and fails on import and seems to conflict with
gi.repository (also, the upstream seems dead).

Fixes #103

setup.py

@@ -23,7 +23,6 @@ setup(name='tuhi',
       python_requires='>=3.6',
       install_requires=[
           'svgwrite',
-          'gi',
           'xdg',
       ]
       )