Screw the bolt into the wedge until it bottoms, then unscrew until it raises about 1/8" or 3mm. Tap it down so it drops. You may have to beat on it , and if so, protect it with a block of wood. You'll know the wedge is free because you can freely lift the bolt the original 1/8" or so.

Note on some short frames, especially if the stem is inserted as far as possible, it's sometimes impossible to push the wedge down because it bottoms against a taper where the steerer tube's wall gets thicker (lower 2" or so on most forks)

If this may apply to you, tap the wedge down as well as you can, work the stem uo a bit, then push the wedge down some more until it's totally free.

If the wedge is free, ie the bolt has free vertical play. but the stem still won't move, it's probably seized because of galvanic corrosion. Search for stuck seatpost threads here for ideas for how to deal with it.