Circular saw would impart a good bit of vibration to the glass panel. Table saw with a well supported workpiece would work better. Might be best, if you really need to do this, to trim it back on the sides using a router and straight edge guide. That said, I agree with u/Alexstarfire, return it and get the correct size door. You could be setting yourself up for heartbreak and frustration by trying to adjust the size of the door.