I don't think there's a way to do this, sorry. I just messed around in a template and not seeing a way to remove them in bulk in a template. If you have a template with a ton of tasks and preds (assuming you do for this situation), my tip is to click into the first task with a predecessor, click backspace to remove it, then hit Enter. You'll jump to the next task's predecessor column and can basically just click backspace, enter, backspace, enter, and you'll get through removing these really quickly!
If this helped you, please mark correct to help others : )