[llvm] [MLGO] Do not include urgent LRs in max cascade calculation (PR #120052)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Dec 16, 10:09 AM EST**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/120052).


https://github.com/llvm/llvm-project/pull/120052