update: quantecon-book-theme 0.12.0 -> 0.13.2 (#443)

Author: mmcky

environment.yml

@@ -7,7 +7,7 @@ dependencies:
   - pip
   - pip:
     - jupyter-book==1.0.4post1
-    - quantecon-book-theme==0.12.0
+    - quantecon-book-theme==0.13.2
     - sphinx-tojupyter==0.6.0
     - sphinxext-rediraffe==0.2.7
     - sphinx-exercise==1.2.1