[llvm] [docs] Stress out the branch naming scheme for Graphite. (PR #104499)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Aug 15, 7:20 PM EDT**: @mtrofin started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/104499).


https://github.com/llvm/llvm-project/pull/104499