[clang] [Clang] Correctly recognize unexpanded packs in lambda template params (PR #98496)

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cor3ntin wrote:

> Thanks. Actually we're missing this flag many times elsewhere in TransformLambdaExpr(). (See my patch #86265, let me try to revive that these days before 19 is cut)

I was not aware of that PR, thanks (The general direction of it looks correct to me.) 
Ah, lambdas, the gift that keeps on giving!

https://github.com/llvm/llvm-project/pull/98496