Remove KELOD banner code and DismissableSiteNotice extension

[tarrow]

This code is already inactive since the deadline passed. Let's clean it up now

[m90]

I'm wondering if we should leave some placeholder version of this in-place so we could reuse it even easier than digging in the git history?

In case we do want to remove it entirely, we probably should also drop the extension itself.

[deer-wmde]

Thanks for making this PR. I think Frederik raised good questions and I guess I lean towards removing the extension again, because if I remember correctly, for future use we wanted to solve this differently. But it's hard to say, my crystal ball is currently out of order 🔮

I could also live with only this conf removed

[m90]

Do we still want to do this?

[tarrow]

both good questions I only bother to reply to after 4 months; I'd suggest we rip out the config and then also remove the extension.

I think while there may be a little digging involved I'd hope that next time we have a banner ticket come in that at a minimum someone searches phabricator for "banner" and "wikibase.cloud" which ought to breadcrumb them into the correct place

[tarrow]

I approve!