migrator: make headers more consistent.

Use `oh1` for moving kegs to a new directory.

Library/Homebrew/migrator.rb

@@ -217,7 +217,7 @@ class Migrator
       end
     end
 
-    puts "Moving to: #{new_cellar}"
+    oh1 "Moving #{Formatter.identifier(oldname)} children"
     if new_cellar.exist?
       FileUtils.mv(old_cellar.children, new_cellar)
     else