The work in {T301096} allows us to configure a `underlinkedWeight` property for the link recommendation task type. By default, articles to be used for link recommendation tasks are selected at random; when `underlinkedWeight` is set, articles with few links (compared to the number of words in the article) are selected with a higher probability. (The exact formaly is given at T301096#8388234.)
We want to progressively roll out the new functionality to different wikis. Per @KStoller-WMF's comment in T301096#8387455, we should first deploy to pilot wikis, wait for / gather feedback, then rollout to all wikis.
In case of problems, the old functionality can be restored simply by removing the `underlinkedWeight` key from the Growth configuration page (`MediaWiki:NewcomerTasks.json`).
**Acceptance Criteria**
[] Prioritization of underlinked articles is enabled on `testwiki` and the four pilot wikis (`arwiki`, `bnwiki`, `cswiki`, `eswiki`).
[] Feedback is gathered from the pilot wikis (and no issues are identified).
[] Prioritization of underlinked articles is enabled by default.