Fix return value of the exit handler

[Rainyan]

autoprocprio/autoprocprio.py

Line 112 in 85c130a

def on_exit(signal_type):

Currently returns None. Should, as per docs, return:

If the function handles the control signal, it should return TRUE. If it returns FALSE, the next handler function in the list of handlers for this process is used.

https://learn.microsoft.com/en-us/windows/console/handlerroutine#return-value