[llvm] [Coroutines] Remove assert about a promise being present (PR #156007)

[Chuanqi Xu via llvm-commits]

ChuanqiXu9 wrote:

> > I am curious about your downstream project using LLVM's coroutine intrinsics.
> 
> We have a complicated flow that I cannot fully disclose here. What is relevant is that we take some input programs without coroutines and convert functions in there to coroutines. Once some IP questions have been resolved, we might publish our use case.

Looking forward for your results : )

https://github.com/llvm/llvm-project/pull/156007