switch to jupyter-book 0.13.0 (which changes several things!)

requirements.txt

 ipympl==0.9.1
 ipython==8.3.0
 ipywidgets==7.7.0
-jupyter==1.0.0
-jupyter-book==0.12.3
+jupyter-book==0.13.0
 jupyter-sphinx==0.3.2
 jupyterthemes==0.20.0
 jupytext==1.13.8