Don't truncate columns on the list of databases

https://covid-19.datasettes.com/covid currently truncates at 9 database columns:

<img width="860" alt="covid" src="https://user-images.githubusercontent.com/9599/120941536-11467d80-c6d8-11eb-970a-ce469623f92c.png">

Django SQL Dashboard showed me that this is a bad idea - having the full list of columns is actually really useful documentation for crafting custom SQL queries.