ci: remove note re M1 usage

M1 is now available in GitHub CI, but we don't currently have a plan to
use it, so remove the comment.

.github/workflows/ci.yml

@@ -71,7 +71,7 @@ jobs:
     name: 'macOS 13 native, x86_64, no depends, sqlite only, gui'
     # Use latest image, but hardcode version to avoid silent upgrades (and breaks).
     # See: https://github.com/actions/runner-images#available-images.
-    runs-on: macos-13  # Use M1 once available https://github.com/github/roadmap/issues/528
+    runs-on: macos-13
 
     # No need to run on the read-only mirror, unless it is a PR.
     if: github.repository != 'bitcoin-core/gui' || github.event_name == 'pull_request'