Most Helpful Guy
It could mean a couple of things. It could mean that he doesn't want you on there anymore or it could be that he wants your attention. People quite often delete people on social media to make a point. They know that person will probably be aware that they've been deleted.
Either way, he's your ex so you should let it go and move forward with your life.
Most Helpful Girl
They can't be bothered with you anymore and is moving on.