Use Python 3.10 for the docs build

Author: parthea

noxfile.py

@@ -120,7 +120,7 @@ def cover(session):
     session.run("coverage", "report", "--show-missing", "--fail-under=100")
 
 
-@nox.session(python="3.9")
+@nox.session(python="3.10")
 def docs(session):
     """Build the docs for this library."""