chore: remove code formatting for noxfile.py

[parthea]

We should ensure that generated code is formatted correctly, rather than relying on external code formatting which increases the overall generation time.

This PR removes code formatting as a separate step for noxfile.py. There were only 3 changes in the file needed to address formatting issues.

We already have a goldens-lint check which checks that the code is formatted properly. This PR avoid the extra step of formatting noxfile.py prior to running the lint check.

IOW, the blacken nox session no longer touches noxfile.py

gapic-generator-python/.github/workflows/tests.yaml

Lines 409 to 414 in f93a0eb

	run: |
	nox -f tests/integration/goldens/asset/noxfile.py -s mypy-${{ env.LATEST_STABLE_PYTHON }} blacken lint
	nox -f tests/integration/goldens/credentials/noxfile.py -s mypy-${{ env.LATEST_STABLE_PYTHON }} blacken lint
	nox -f tests/integration/goldens/eventarc/noxfile.py -s mypy-${{ env.LATEST_STABLE_PYTHON }} blacken lint
	nox -f tests/integration/goldens/logging/noxfile.py -s mypy-${{ env.LATEST_STABLE_PYTHON }} blacken lint
	nox -f tests/integration/goldens/redis/noxfile.py -s mypy-${{ env.LATEST_STABLE_PYTHON }} blacken lint

[chalmerlowe]

LGTM