Shania Twain may not hold a grudge — but she won’t forget about the way she was treated by her ex-husband. While recently on Jamie Laing’s “Great Company” podcast, the 58-year-old country singer spoke about her relationship with ex-husband Robert “Mutt” Lange — 16 years after he cheated on her with then-BFF Marie-Anne Thiebaud. “Forgiveness is in the family of letting go. But forgiveness, more specifically for me anyway, is not about forgetting necessarily,” she shared about the 2008 incident, which led her to marry Marie-Anne’s ex Frederic Thiebaud. “It’s about understanding the other person,…