[clang] [clang] Cover CWG issues about `export template` (PR #94876)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

Me and Corentin discussed this offline. Two points emerged there:
1) He's more concerned with the fact that 204 and other Core issues are highlighted green, inheriting the status of the issue that superseded them, than with the fact that they are marked as superseded. Styles we use in `cxx_dr_status.html` can be changed in a subsequent PR.
2) In previous discussions on this topic, I remember that we together with @AaronBallman agreed that statuses on our page should follow the official statuses. This PR goes against it, because I know from experience that the current CWG chair is not interested in revisiting Core issues that were closed long ago, and mark them as superseded where appropriate. We might need to revisit out previous consensus in the light of this PR and aforementioned experience talking to Core.

https://github.com/llvm/llvm-project/pull/94876