chore(python): fix formatting issue in noxfile.py.j2

[parthea]

PR #1237 fixed a formatting issue in noxfile.py.j2 however after running the latest post processor image, there is still a syntax issue.

Here are the steps that I ran to validate this fix.

Checkout the branch for this PR and run the following:

docker build -t testlogging -f docker/owlbot/python/Dockerfile .

In the python-logging repo, run

docker run --user $(id -u):$(id -g) --rm -v $(pwd):/repo -w /repo testlogging