DEV: remove instagram login site settings and auth classes. (PR #11073)

Instagram removed the support for oauth2 login and should use Facebook login instead.

GitHub

This pull request has been mentioned on Discourse Meta. There might be relevant details there:

https://meta.discourse.org/t/remove-enable-instagram-logins-since-its-not-relevant-anymore/167726/5

Failure is legit, @vinothkannans … once you sort it you are good to merge

  1. Jobs::OldKeysReminder sends message to admin with old credentials Failure/Error: