[clang] [clang] Document CWG3129 as resolved (PR #206335)

[Jan Schultke via cfe-commits]

eisenwave wrote:

> You need to take your tests to Compiler Explorer to see what was the first Clang release that exhibited the expected behavior (call it R).

I've tried that, and I couldn't find a version old enough where it wouldn't do that. My impression is that 2.7 is being used to mean "since forever" in these issue resolutions, but that's so old, it's not even on Compiler Explorer.

https://github.com/llvm/llvm-project/pull/206335