Add django-tables2 to dev dependencies

conftest.py imports django_tables2 to build _FakeBaseTable, but it was
missing from the dev extras, causing CI to abort before collecting tests.

Author: Kani999

pyproject.toml

@@ -25,7 +25,7 @@ classifiers = [
 dependencies = []
 
 [project.optional-dependencies]
-dev = ["pytest", "pytest-django", "ruff"]
+dev = ["pytest", "pytest-django", "ruff", "django-tables2"]
 
 [project.urls]
 Homepage = "https://github.com/CESNET/netbox-custom-objects-tab"