MINOR: Fix typo in processor api developer guide (#12203)
MINOR: Fix typo in processor api developer guide (#12203)

The reference to `changlogConfig` should be `changelogConfig`.

Reviewers: Jason Gustafson <68c46a606457643eab92053c1c05574abb26f861@confluent.io>
apache/kafka,lindong28/kafka,lindong28/kafka,guozhangwang/kafka,guozhangwang/kafka,apache/kafka,guozhangwang/kafka,apache/kafka,apache/kafka,lindong28/kafka,guozhangwang/kafka,lindong28/kafka