[clang] [Clang] Fix P2564 handling of variable initializers (PR #89565)

[Daniel M. Katz via cfe-commits]

katzdm wrote:

> @katzdm Does it make sense to file an issue so we don't forget to bring the warning back?

Yep, for sure - I've opened #92656.

https://github.com/llvm/llvm-project/pull/89565