package/python-gobject: depend on python2

Version 2.86.6 of python-gobject is quite old and no longer works with
Python versions > 3.7. When importing a user will recieve the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.8/site-packages/gobject/__init__.py", line 26, in
  <module>
  File "/usr/lib/python3.8/site-packages/glib/__init__.py", line 22, in <module>
SystemError: initialization of _glib raised unreported exception

Because new versions of python-gobject require gobject-introspection, which is
not currently available in Buildroot, add a dependency on python2 to prevent
users from receiving the above error.

Fixes: https://bugs.busybox.net/show_bug.cgi?id=12286



Signed-off-by: Adam Duskett <Aduskett@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>