operator.update, columns in where cant be updated

[sunfuze]

https://github.com/ali-sdk/ali-rds/blob/master/lib/operator.js#L161
code here will filter columns in where.

...
for (let i = 0; i < options.columns.length; i++) {
  const column = options.columns[i];
  // below here filter column in where
  if (column in options.where) {
    continue;
  }
  sets.push('?? = ?');
  values.push(column);
  values.push(row[column]);
}
...