upgrade to sphinx-tojupyter==0.3.1

Author: mmcky

environment.yml

@@ -8,7 +8,7 @@ dependencies:
   - pip:
     - jupyter-book==1.0.4post1
     - quantecon-book-theme==0.8.3
-    - sphinx-tojupyter==0.3.0
+    - sphinx-tojupyter==0.3.1
     - sphinxext-rediraffe==0.2.7
     - sphinx-exercise==1.0.1
     - sphinxcontrib-youtube==1.4.1