extmod/modbtree: Rename "sync" method to "flush" for consistency.
extmod/modbtree: Rename "sync" method to "flush" for consistency.

Rename recently introduced "sync" method to "flush" for consistency with
usual files.

swegener/micropython,alex-robbins/micropython,tobbad/micropython,SHA2017-badge/micropython-esp32,toolmacher/micropython,Timmenem/micropython,lowRISC/micropython,MrSurly/micropython,tuc-osg/micropython,TDAbboud/micropython,adafruit/micropython,lowRISC/micropython,blazewicz/micropython,oopy/micropython,tobbad/micropython,torwag/micropython,MrSurly/micropython,tralamazza/micropython,hiway/micropython,swegener/micropython,oopy/micropython,trezor/micropython,Peetz0r/micropython-esp32,ryannathans/micropython,MrSurly/micropython,lowRISC/micropython,torwag/micropython,pozetroninc/micropython,henriknelson/micropython,TDAbboud/micropython,swegener/micropython,HenrikSolver/micropython,tralamazza/micropython,dmazzella/micropython,puuu/micropython,HenrikSolver/micropython,SHA2017-badge/micropython-esp32,MrSurly/micropython,SHA2017-badge/micropython-esp32,cwyark/micropython,trezor/micropython,MrSurly/micropython-esp32,pramasoul/micropython,henriknelson/micropython,kerneltask/micropython,micropython/micropython-esp32,mhoffma/micropython,HenrikSolver/micropython,chrisdearman/micropython,bvernoux/micropython,blazewicz/micropython,chrisdearman/micropython,MrSurly/micropython-esp32,cwyark/micropython,chrisdearman/micropython,HenrikSolver/micropython,tuc-osg/micropython,oopy/micropython,PappaPeppar/micropython,AriZuu/micropython,bvernoux/micropython,adafruit/circuitpython,TDAbboud/micropython,hiway/micropython,cwyark/micropython,trezor/micropython,ryannathans/micropython,tobbad/micropython,micropython/micropython-esp32,micropython/micropython-esp32,pramasoul/micropython,adafruit/circuitpython,AriZuu/micropython,alex-robbins/micropython,pozetroninc/micropython,adafruit/circuitpython,MrSurly/micropython-esp32,lowRISC/micropython,bvernoux/micropython,toolmacher/micropython,pozetroninc/micropython,alex-robbins/micropython,tuc-osg/micropython,kerneltask/micropython,TDAbboud/micropython,PappaPeppar/micropython,mhoffma/micropython,torwag/micropython,adafruit/micropython,infinnovation/micropython,PappaPeppar/micropython,hiway/micropython,ryannathans/micropython,toolmacher/micropython,selste/micropython,pfalcon/micropython,mhoffma/micropython,HenrikSolver/micropython,toolmacher/micropython,dmazzella/micropython,SHA2017-badge/micropython-esp32,hiway/micropython,chrisdearman/micropython,adafruit/circuitpython,SHA2017-badge/micropython-esp32,torwag/micropython,tobbad/micropython,pfalcon/micropython,cwyark/micropython,puuu/micropython,tuc-osg/micropython,henriknelson/micropython,torwag/micropython,tralamazza/micropython,AriZuu/micropython,pozetroninc/micropython,trezor/micropython,deshipu/micropython,adafruit/micropython,pramasoul/micropython,toolmacher/micropython,pramasoul/micropython,mhoffma/micropython,swegener/micropython,puuu/micropython,pramasoul/micropython,selste/micropython,PappaPeppar/micropython,deshipu/micropython,bvernoux/micropython,ryannathans/micropython,pfalcon/micropython,MrSurly/micropython,Peetz0r/micropython-esp32,pfalcon/micropython,alex-robbins/micropython,tuc-osg/micropython,adafruit/circuitpython,tobbad/micropython,lowRISC/micropython,Timmenem/micropython,adafruit/micropython,dmazzella/micropython,hiway/micropython,micropython/micropython-esp32,Peetz0r/micropython-esp32,oopy/micropython,infinnovation/micropython,MrSurly/micropython-esp32,infinnovation/micropython,swegener/micropython,oopy/micropython,Peetz0r/micropython-esp32,Timmenem/micropython,ryannathans/micropython,TDAbboud/micropython,deshipu/micropython,adafruit/micropython,dmazzella/micropython,chrisdearman/micropython,mhoffma/micropython,infinnovation/micropython,puuu/micropython,alex-robbins/micropython,kerneltask/micropython,henriknelson/micropython,AriZuu/micropython,pozetroninc/micropython,kerneltask/micropython,kerneltask/micropython,Timmenem/micropython,tralamazza/micropython,adafruit/circuitpython,deshipu/micropython,micropython/micropython-esp32,trezor/micropython,puuu/micropython,selste/micropython,blazewicz/micropython,cwyark/micropython,selste/micropython,MrSurly/micropython-esp32,blazewicz/micropython,bvernoux/micropython,henriknelson/micropython,blazewicz/micropython,selste/micropython,infinnovation/micropython,Peetz0r/micropython-esp32,pfalcon/micropython,deshipu/micropython,PappaPeppar/micropython,AriZuu/micropython,Timmenem/micropython