[llvm] [llvm][Comment] removing out-of-date comment, ARM backend no longer uses ScheduleDAGRRList (PR #117803)

[Matthias Braun via llvm-commits]

MatzeB wrote:

Also find it hard to believe that ARM, or any backend for that matter has 100% switched from SelectionDAG to GlobalISel. I thought they are all stuck somewhere in-between (but admittedly I did not follow this development closely).

https://github.com/llvm/llvm-project/pull/117803