extmod/vfs_fat: Remove declaration of mp_builtin_open_obj.
extmod/vfs_fat: Remove declaration of mp_builtin_open_obj.

It's declared already in py/builtin.h.

trezor/micropython,pfalcon/micropython,pozetroninc/micropython,adafruit/micropython,bvernoux/micropython,MrSurly/micropython,henriknelson/micropython,adafruit/circuitpython,swegener/micropython,adafruit/circuitpython,selste/micropython,adafruit/micropython,pozetroninc/micropython,ryannathans/micropython,henriknelson/micropython,tralamazza/micropython,adafruit/micropython,tralamazza/micropython,pfalcon/micropython,tralamazza/micropython,selste/micropython,tobbad/micropython,henriknelson/micropython,MrSurly/micropython,pramasoul/micropython,tobbad/micropython,kerneltask/micropython,pozetroninc/micropython,pozetroninc/micropython,adafruit/micropython,dmazzella/micropython,kerneltask/micropython,dmazzella/micropython,selste/micropython,bvernoux/micropython,tobbad/micropython,adafruit/circuitpython,ryannathans/micropython,swegener/micropython,MrSurly/micropython,kerneltask/micropython,MrSurly/micropython,trezor/micropython,ryannathans/micropython,pozetroninc/micropython,bvernoux/micropython,tobbad/micropython,tralamazza/micropython,trezor/micropython,dmazzella/micropython,selste/micropython,ryannathans/micropython,pfalcon/micropython,tobbad/micropython,pfalcon/micropython,swegener/micropython,henriknelson/micropython,pramasoul/micropython,trezor/micropython,henriknelson/micropython,pramasoul/micropython,pfalcon/micropython,kerneltask/micropython,ryannathans/micropython,adafruit/micropython,swegener/micropython,selste/micropython,dmazzella/micropython,pramasoul/micropython,bvernoux/micropython,swegener/micropython,bvernoux/micropython,adafruit/circuitpython,MrSurly/micropython,trezor/micropython,pramasoul/micropython,adafruit/circuitpython,kerneltask/micropython,adafruit/circuitpython