fix: Upgrade python-gitlab range

Keeping both 1.x and 2.x since only change that is breaking is dropping
python 3.6 support. I hope that leaving the lower limit will make it
still work with python 3.6.

Fixes #329

setup.py

@@ -42,7 +42,7 @@ def _read_long_description():
         "twine>=3,<4",
         "requests>=2.25,<3",
         "wheel",
-        "python-gitlab>=1.10,<2",
+        "python-gitlab>=1.10,<3",
         "tomlkit>=0.7.0,<1.0.0",
         "dotty-dict>=1.3.0,<2",
     ],