Remove the end cap and then the striker. The slide is being held in place by the protrusion on the striker (the part that engages the sear).
You can pull the slide to the rear far enough to get to the striker, insert a small screwdriver to push forward on the strike sleeve, which reduces the pressure on the end cap and lets it slide out. Then the striker slides out. Then the slide glides off.
I think this will work.