Update walmart funded incentives enrollment

ThewalmartFundedIncentivesEnrollmentAPI allows sellers to modify their enrollment status and details for Walmart-funded incentives programs. While all Walmart-funded incentives are auto-enrolled by default, you can use this API to 'Opt-out' specific Walmart-funded items whose price you don't wish to lower. You can also 'Opt-in' items which were previously Opted-out by you at any time using this API.