text: Title: [DOC] International Teacher Data notebook should not have 1st-level markdown beyond title
  Body: # Brief Description of Fix
  
  Currently, the example on [Processing International Teacher data](https://pyjanitor.readthedocs.io/notebooks/teacher_pupil.html) has two top-level markdown titles: One for `Processing International Teacher Data`, and the other for `Data Dictionary`. 
  
  I would like to propose a change, such that `Data Dictionary` gets demoted to 2nd level. This would prevent it from showing up on the navigation tab of the docs.
  
  # Relevant Context
  
  <!-- Please put here, in bullet points, links to the relevant docs page. A few starting template points are available
  to get you started. -->
  
  - [Link to documentation page](https://pyjanitor.readthedocs.io/notebooks/teacher_pupil.html#Data-Dictionary)
  - [Link to exact file to be edited](https://github.com/ericmjl/pyjanitor/blob/dev/examples/notebooks/teacher_pupil.ipynb)
  