scoop-update.ps1: Use internal s/get_config function instead of scoop cmd (#3061)
scoop-update.ps1: Use internal s/get_config function instead of scoop cmd (#3061)

This will prevent `Scoop is not recognized as internal command` when updating.
kodybrown/scoop,rasa/scoop,coonce/scoop,nikolasd/scoop,berwyn/scoop,lukesampson/scoop