Require PyGObject before 3.51

The GenericTreeModel from pygtkcompat has been removed.

#13855
(grafted from d7050674aabe4ecc3c986f6ab7a474ab4f89afcf)

--HG--
branch : 6.0

tryton/setup.py

@@ -130,7 +130,7 @@ dist = setup(name=name,
     install_requires=[
         'pycairo',
         "python-dateutil",
-        'PyGObject>=3.19',
+        'PyGObject>=3.19,<3.51',
         ],
     extras_require={
         'calendar': ['GooCalendar>=0.7'],