ads_bibdesk is likely broken

[keflavich]

With the final, permanent deprecation of the old ADS UI, it appears that the download machinery in ads_bibdesk is broken. We either need to majorly refactor or call this software dead. A refactor could use https://github.com/r-xue/ads2bibdesk or https://bibmanager.readthedocs.io/en/latest/ or we might just tell people to go there.