updates blacken to 3.10

Author: chalmerlowe

noxfile.py

@@ -103,7 +103,11 @@ def lint(session):
     session.run("flake8", "db_dtypes", "tests")
 
 
-@nox.session(python="3.8")
+# TODO: the owlbot-python docker image still has python 3.8 installed (
+# and only 3.8).
+# As soon as that gets upgraded, we should be able to revert this session
+# to using the DEFAULT_PYTHON_VERSION.
+@nox.session(python="3.10")
 def blacken(session):
     """Run black. Format code to uniform standard."""
     session.install(BLACK_VERSION)