This issue still exists, the offending line can be found here:

https://github.com/wikimedia/mediawiki-extensions-CentralNotice/blob/ed8a7c3b8e92a48f7c4286360bc91dce86148345/i18n/en.json#L210

6 years for such a small thing, wow.

As someone who doesn't know CentralNotice could someone explain what this is about? This seems like a good candidate for good first task only but the problem doesn't seem to be well defined.

The url 404s because it's a bad URL and should be
https://github.com/wikimedia/mediawiki-extensions-CentralNotice/blob/master/resources/ext.centralNotice.bannerController/mobile/device.js

Presumably something links to it? Is there a screenshot or code that can give a clue to a volunteer about how to fix it?

@Jdlrobson, there are some additional details in the linked duplicate bug, and there is link to the position in code where the change needs to be done in the comment above.