[llvm] [Docs] Update Maintainer in Developer Policy (PR #154687)

[Jacques Pienaar via llvm-commits]

https://github.com/jpienaar commented:

Perhaps question on order. I expected the discussions in the doc to be part of drafting process (and I know there are other such discussions ongoing, so its not even the only proposal in progress), post that post on discord with RFC (refined version of doc, still open for comments as difference in visibility and who can comment), post that (which includes discussions) a PR. But we have a PR already here too, so where should discussions happen?

https://github.com/llvm/llvm-project/pull/154687