Pin Python version

Author: davidhassell

DOCUMENTATION.md

@@ -1,4 +1,4 @@
-* The generation of recipes using Sphinx-Gallery requires:
+* The generation of recipes using Sphinx-Gallery requires `Python<3.12.0` and:
 
   ```txt
   pip install sphinx-gallery==0.11.0
@@ -10,6 +10,7 @@
   pip install sphinxcontrib-devhelp==1.0.2
   pip install sphinxcontrib-serializinghtml==1.1.3
   pip install sphinxcontrib-qthelp==1.0.3
+  ip install sphinxcontrib.applehelp==1.0.4
   pip install alabaster==0.7.13
   pip install sphinx==2.4.5
   ```