Steelcase lists the arm rests on their Leap chairs as “factory installed” and not removable, perhaps because the brackets supporting the arms also support the backrest. In the event you must ever remove the arms, perhaps because your wife decides she’d like to try the chair without them, it’s straightforward.
Loosen the Torx screw visible through the slot in the bottom of the plastic shroud about a dozen turns (it will not click or feel loose), use a flat screwdriver to unlock the shroud from the flat plastic plate on the seat side of the bracket, then forcibly pull the sides of the shroud outward until you can pull the arm extension mechanism up-and-out of these slots in the bracket:
This view from the side of the chair shows the screw hole in the bottom, with a pair of holes for alignment pins beside it:
You can remove the flat plate by pushing the latch at the top center (just below the backrest screw boss), then sliding the plate upward.
As nearly as I can tell, there’s no way to remove the shroud from around the arm extension mechanism, so you must pull off the whole thing in one lump:
The two pairs of slots in the edges of the shroud engage tabs on the plastic plate; that’s why you need the flat screwdriver.
The two pins on the bottom lock the arm into the bracket: you must raise it vertically until those come out, after which you can ease the bottom outward until the pins on the sides (which you can’t see inside the shroud) disengage from the bracket slots.
It takes a whole lot more force than seems necessary, but it can be done.
Wrap Gorilla tape around the raw edges until you decide whether it’s worthwhile to design and print a pair of plastic caps to cover the whole bracket.