Use 'rated' as default preferred range

The changes in 896e679 had no effect on new installations.

priv/repo/migrations/20190913165850_add_range_enum.exs

@@ -7,7 +7,7 @@ defmodule TeslaMate.Repo.Migrations.AddRangeEnum do
     Range.create_type()
 
     alter table(:settings) do
-      add(:preferred_range, Range.type(), default: "ideal", null: false)
+      add(:preferred_range, Range.type(), default: "rated", null: false)
     end
   end
 end