This is a continuation of
https://github.com/discourse/discourse/pull/36885.
The rake task here backfills `topic_localization.excerpt` which may have
been empty (both `nil` and `""` are valid as checked on meta).
The reason why this can't be a migration is because we use
`Post.excerpt` which taps on a method in the post model which also uses
`PrettyText`.
