setup.cfg: bump version to 2.3.5 (#605)

Procedure:
```
$ python3 setup.py sdist
...
$ python3 setup.py bdist_wheel
...
$ python3 -m twine check --strict dist/*
Checking dist/pylxd-2.3.5-py3-none-any.whl: PASSED
Checking dist/pylxd-2.3.5.tar.gz: PASSED

# upload to testpypi
$ python3 -m twine upload --repository pylxd-testpypi dist/*
Uploading distributions to https://test.pypi.org/legacy/
Uploading pylxd-2.3.5-py3-none-any.whl
100% ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 105.5/105.5 kB • 00:00 • 188.8 MB/s
Uploading pylxd-2.3.5.tar.gz
100% ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 79.1/79.1 kB • 00:00 • 189.9 MB/s

View at:
https://test.pypi.org/project/pylxd/2.3.5/
```

The test upload is available at
https://test.pypi.org/project/pylxd/2.3.5/

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = pylxd
-version = 2.3.4
+version = 2.3.5
 description = python library for LXD
 long_description = file: README.rst
 long_description_content_type = text/x-rst