Always add Overview to the category hash map to display it as a subtitle (#1789)
Always add Overview to the category hash map to display it as a subtitle (#1789)

Always add Overview to the category hash map. This ensures that is
displayed as a subtitle and translated to other languages.

Fixes the bug introduced by
https://github.com/datacommonsorg/website/pull/1754

Bug: b/206032102


![image](https://user-images.githubusercontent.com/109985835/195956766-01f5cea3-f2a9-46b2-9c80-02525d2794d5.png)
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