var quotasSearch = search.load(QUOTAS);
for (var i = 0; i < quotasSearch.filters.length; i++) {
    if (quotasSearch.filters[i].name === 'custrecord_sales_rep') {
        log.debug('here', 'popping');
        quotasSearch.filters.pop(i);
    }
}
var salesRepIsEmp = search.createFilter({name: 'custrecord_sales_rep', operator: search.Operator.ANYOF, values: [employee]});
log.debug('before', quotasSearch.filters);
quotasSearch.filters.push(salesRepIsEmp);
log.debug('after', quotasSearch.filters);