Update notification.js

"The callback takes the argument buttonIndex (Number), which is the index of the pressed button. Note that the index uses one-based indexing, so the value is 1, 2, 3, etc."

callback 0 is reserved for the buttons turns the platforms that exist these buttons.

before: 
button index 0 return 0 in callback; - YES
button index 1 return 1 in callback; - NO

after:
button index 0 return 1 in callback; - YES
button index 0 return 1 in callback; - NO