From T360668#10176602

In T360668 we dropped support for legacy message box HTML.
While a special module was added to the page to target HTML using it, it doesn't apply to JS.

Impacted line: https://gerrit.wikimedia.org/g/mediawiki/extensions/CentralNotice/+/b0a196822c54b931f08b6a8ff403345ad418badb/resources/infrastructure/campaignManager.js#559

TODO

• On short term please load mediawiki.legacy.messageBox
• On long term please use Codex markup. A possible stable API may be introduced as part of https://gerrit.wikimedia.org/r/c/mediawiki/core/+/1075626