I was trying to remove them all by following the instructions on
Clearing All Tabs in a Document (Microsoft Word). But that didn't work.
But what did work was to go to Find&Replace. In the Find box, I searched for ` ^t ` (without the tick marks). I found this code by clicking "Special..." at the bottom of the Search&Replace box. Then, in the Replace blank, I had one space (one tap of the spacebar). That solved my problem.