Update example to mention allowedReportingOrigins (#1373)

allowedReportingOrigins is mentioned in the next section, but missing from the example.

FLEDGE.md

@@ -142,7 +142,8 @@ const myGroup = {
           {renderUrl: shoesAd2, sizeGroup: 'group2',
            selectableBuyerAndSellerReportingIds: ['deal1', 'deal2', 'deal3'],
            buyerReportingId: 'buyerSpecificInfo1',
-           buyerAndSellerReportingId: 'seatId', ...}],
+           buyerAndSellerReportingId: 'seatId',
+           allowedReportingOrigins: ['https://example-reporter.com'], ...}],
   'adComponents': [{renderUrl: runningShoes1, sizeGroup: 'group2', ...},
                    {renderUrl: runningShoes2, sizeGroup: 'group2', ...},
                    {renderUrl: gymShoes, sizeGroup; 'group2', ...}],