KAFKA-13172: Add downgrade guidance note for 3.0 (#11184)
KAFKA-13172: Add downgrade guidance note for 3.0 (#11184)

Reviewers: Luke Chen <a747209bc9e65a9d7dd7589245c91b7bed721b13@gmail.com>, Anna Sophie Blee-Goldman <ableegoldman@apache.org>, Bruno Cadonna <cadonna@confluent.io>
lindong28/kafka,guozhangwang/kafka,lindong28/kafka,TiVo/kafka,apache/kafka,guozhangwang/kafka,TiVo/kafka,apache/kafka,apache/kafka,TiVo/kafka,guozhangwang/kafka,lindong28/kafka,TiVo/kafka,lindong28/kafka,apache/kafka,guozhangwang/kafka