Which payment method is most comonly used by the schools in the state of Georgia for the payment of donations?
Georgia refer to school_state = 'GA'

SELECT T1.payment_method FROM donations AS T1 INNER JOIN projects AS T2 ON T1.projectid = T2.projectid WHERE T2.school_state = 'GA' GROUP BY T2.school_state ORDER BY COUNT(T1.payment_method) DESC LIMIT 1