[llvm] [Instrumentation] Fix EdgeCounts vector size in SetBranchWeights (PR #99064)

[Avi Kivity via llvm-commits]

avikivity wrote:

> > Thanks a lot @ellishg and @mtrofin for your help and guidance.
> > 
> > Can this please be backported to release/19.x?
> 
> @tstellar for the release bit. @tstellar happy to help, is this more than cherrypicking to a particular branch?

It's just cherrypicking. I already know it backports directly to 18.x, so 19.x should work too. 

https://github.com/llvm/llvm-project/pull/99064