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

[parthea]

This PR fixes the issue reported in googleapis/repo-automation-bots#2669, where the owlbot post processor fails due to a syntax issue.

With the existing noxfile.py.j2, the following code is generated for googleapis/python-logging

session.install("flask", "-c", constraints_path)session.install("webob", "-c", constraints_path)session.install("django", "-c", constraints_path)

Using the changes in this PR, the syntax issue appears to be fixed.

Steps to reproduce:

1. In the root of the googleapis/synthtool repo, run docker build -t testpostprocessor -f docker/owlbot/python/Dockerfile .
2. In the root of the googleapis/python-logging repo, run docker run --user $(id -u):$(id -g) --rm -v $(pwd):/repo -w /repo testpostprocessor
3. The above step should produce the following error owlbot-python: post-processor crashing update lock jobs repo-automation-bots#2669

To confirm this fix, repeat the above steps with the fixes in this PR.

Fixes googleapis/repo-automation-bots#2669