Bump hacking

hacking 3.0.x is too old. Bump it to the version currently used in
tempest repo.

Depends-on: https://review.opendev.org/c/openstack/tempest/+/906634
Change-Id: Id322cc95f16279c26af8b239a685b23b9bd119b9
diff --git a/tox.ini b/tox.ini
index e23dbc8..558e6f8 100644
--- a/tox.ini
+++ b/tox.ini
@@ -20,7 +20,7 @@
 commands = stestr run {posargs}
 
 [testenv:pep8]
-deps = hacking>=3.0,<3.1.0
+deps = hacking>=6.1.0,<6.2.0
 commands = flake8 {posargs}
 
 [testenv:venv]