With the next release just around the corner, legacy OpenID 2.0 support has been removed from Discourse core. This wasn’t being used by core or any official plugins, and the deprecation notice has been around since April 2019.
Just in case anyone hasn’t seen the deprecation notice, the database table containing account associations has not yet been dropped. Any attempt to access it via ActiveRecord will raise an exception. It will be dropped before v2.5