You might see if you can see any model number, operating voltage or frequency range on the fan itself. It might not be happy if you remove the capacitor depending upon the characteristics of the fan. A capacitor run motor is most commonly indicated by extra wires coming out of the fan connecting to the capacitor.
If the fan is operating normally why not leave the capacitor in there if it is not bothering anything?
I replaced my fans with normal 120 volt 50-60 Hz ones since they were making a lot of bearing noise and have reached end-of-life anyway. Then you can remove any labels referring to the 400 Hz operation of the unit..
Greg
