We used to duplicate the data in these fields between them and TextLogErrorMetadata's versions. A recent change moved us to only using TextLogErrorMetadata's version so these can be dropped. Django's migrations naively try to remove them the columns with two ALTER TABLE statements so we'll need to both remove the FK constraint from best_classification then create an SQL migration to drop the columns at the same time.

Comment on attachment 8987002 [details] Remove FailureLine's best_classification and best_is_verified Cancelling pending https://github.com/mozilla/treeherder/pull/3687#pullrequestreview-131179194