Normalize COD from General Bills

[jmotis]

Noting it impacts the following visualizations or menus:

• https://deathbynumbers.org/visualizations/causes-histogram/
• https://deathbynumbers.org/visualizations/sparklines-causes-general/
• https://deathbynumbers.org/visualizations/wordcloud/
• https://deathbynumbers.org/visualizations/causes-seasonality/
• https://deathbynumbers.org/visualizations/deaths-general/