Remove duplicate feed already in the NABSA systems.csv

The URLs differ, but since we now support version updates they end up on
the same feed eventually.

src/tools/gbfs-feeds.txt

 https://api.openbike.ulm.dev/gbfs/gbfs.json
 https://mds.bird.co/gbfs/v2/public/ulm/gbfs.json
-https://mds.bird.co/gbfs/chicago/gbfs.json
 https://www.bolt.miami/bolt2/chi/gbfs/gbfs.json
 https://portal.clevrmobility.com/api/gbfs/chicago/en/discovery/?format=json
 https://gbfs.uber.com/v1/chicago/gbfs.json