package/python-twisted: add missing python typing extensions runtime dependency

# python sample_python_txtorcon.py
 Traceback (most recent call last):
   File "/root/sample_python_txtorcon.py", line 1, in <module>
     import txtorcon  # noqa
   File "/usr/lib/python3.10/site-packages/txtorcon/__init__.py", line 11, in <module>
   File "/usr/lib/python3.10/site-packages/txtorcon/router.py", line 10, in <module>
   File "/usr/lib/python3.10/site-packages/txtorcon/util.py", line 17, in <module>
   File "/usr/lib/python3.10/site-packages/twisted/internet/defer.py", line 42, in <module>
 ModuleNotFoundError: No module named 'typing_extensions'

python typing_extensions is required since python-twisted 22.1.0 [1]

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/2116202537

[1] https://github.com/twisted/twisted/commit/6e768da0a10c8ab42a57a1c0fa505ebe2d8bfb30



Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>