Is it normal to develop seroma at the incision site after a surgical hysterectomy?

Common. That is not uncommon and may resolve on is own. Sometimes the seroma will open and drain on it's own, sometimes they must be opened and drained. It may be inconvenient but is not considered to be a severe complication.
Seroma. A seroma is a sterile collection of fluid that fills in a wound. Sometimes they resolve on their own other times they have to be drained. Sometimes a surgeon will leave a drain in place after surgery to try and prevent them. They may not be "normal" but are quite common after surgical procedures.