update blacken

Author: ohmayr

owlbot.py

@@ -337,4 +337,4 @@ def get_staging_dirs(
 
 # Use a python runtime which is available in the owlbot post processor here
 # https://github.com/googleapis/synthtool/blob/master/docker/owlbot/python/Dockerfile
-s.shell.run(["nox", "-s", "blacken-3.10"], hide_output=False)
+s.shell.run(["nox", "-s", "blacken"], hide_output=False)