Repository language is not updated anymore

Created by: sqs

In https://sourcegraph.com/github.com/sourcegraph/sourcegraph/-/commit/0a137981f3628128a3952cb1ea79681ac3e5f7bf we removed the code that updated the repo.language DB column, so GraphQL-querying Repository.language will return empty for newly added repositories (and the previous, possibly stale language for repositories that existed before that commit).