ci(network-traffic-analyzer): drop ruff preview to keep lint green across versions

The lint job installs ruff unpinned (pip install ruff), which reached 0.15.22
and, under preview = true, promoted the rule-codes-in-selectors diagnostic that
rejects rule codes like E501/S101 in lint.ignore. This project was the only one
with preview enabled. Dropping preview keeps the code-based selectors valid on
every ruff version in play (0.15.1 pre-commit pin, 0.15.7, 0.15.22 CI) and
aligns it with the other Python projects. No rule coverage change.

PROJECTS/beginner/network-traffic-analyzer/python/pyproject.toml

@@ -44,7 +44,6 @@ packages = [
 [tool.ruff]
 target-version = "py314"
 line-length = 88
-preview = true
 src = [
     "src/netanal",
 ]