With the door panel off, crank the window down while peeking into the access hole on the rear gear. You'll see a set screw about 1 inch from the outside edge of the gear. If it's an "original" regulator it will be a slotted screw with a head about 1/8" thick. That screw acts as a "down stop" to keep the rollers inside the tracks of the window channel.
Hold the glass from the top so it does not drop down into the door, then continue cranking the regulator down until the rollers come out of the channel. Sometimes, and I don't know why, you have to remove the regulator mounting screws and wiggle things to get the rollers to come out.
The glass should then lift out the top of the door.