In order to undo this change you must:
1. Go to SQLYog (or whatever similar program you are using).
2. Find, under mangos, the table "creature_template".
3. Right click, "Alter table...".
4. Select one of the new columns (PowerType, spell 5, spell 6, spell 7, spell 8, VehicleId) and click "Delete" at the bottom.
5. When you have finished with all six columns, click on "Alter".
Anyway, I'm still trying to figure out how to make this patch work. If I find the answer, I'll post it for others with the same problem.