[llvm] [Target] Change `no-trap-after-noreturn` to `trap-after-noreturn` (PR #67925)

[Christian Sigg via llvm-commits]

chsigg wrote:

I had considered that, but didn't like the idea of variable names not matching the flag name. I also think Nikita's concerns would still apply, because it's common to configure this through TargetOptions, not through command line arguments.

https://github.com/llvm/llvm-project/pull/67925