removes `get_credit_days` function as it is no longer useful
removes `get_credit_days` function as it is no longer useful

indictranstech/erpnext,gsnbng/erpnext,indictranstech/erpnext,gsnbng/erpnext,gsnbng/erpnext,indictranstech/erpnext,indictranstech/erpnext,gsnbng/erpnext