Reshuffle additional python for data analysis content into short courses

Author: liamjberrisford

_toc.yml

@@ -335,6 +335,8 @@ parts:
       - file: short_courses/python
         sections:
           - file: short_courses/python_environments
+          - file: short_courses/python_language_features
+          - file: short_courses/python_testing
       - file: short_courses/r
         sections:
           - file: short_courses/r_environments