WIP: update.nix: use Unicode arrow

maintainers/scripts/update.py

···
         # Git can only handle a single index operation at a time
         async with merge_lock:
             await check_subprocess_output("git", "add", *change["files"], cwd=worktree)
-            commit_message = "{attrPath}: {oldVersion} -> {newVersion}".format(**change)
+            commit_message = "{attrPath}: {oldVersion} → {newVersion}".format(**change)
             if "commitMessage" in change:
                 commit_message = change["commitMessage"]
             elif "commitBody" in change: