[clang] [Sema] Preserve ContainsUnexpandedParameterPack in TransformLambdaExpr (PR #86265)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

> I was waiting for the CI, but it seems Linux CI would take hours. However that shouldn't block the review I think, because Windows CI is green now.

FWIW Linux CI is recovering as we speak. I expect full recovery over the weekend.

https://github.com/llvm/llvm-project/pull/86265