[llvm] [DirectX] fix illegal behavior flag in module flags. (PR #96577)

[Joshua Batista via llvm-commits]

bob80905 wrote:

> Could you explain why the flag behavior is set to warning? If I understand, you have 6 options to choose from, so why pick that one?

I read the issue, I think I get it now. 

https://github.com/llvm/llvm-project/pull/96577