Vim: remove unused number keypad mappings
Vim: remove unused number keypad mappings

Should have done this years ago, as I haven't used a keyboard with a
separate number keypad since 2013.

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent