MINOR: Add upgrade docs for 2.4.0 release
MINOR: Add upgrade docs for 2.4.0 release

Author: Manikumar Reddy <manikumar.reddy@gmail.com>

Reviewers: Reviewers: Manikumar Reddy <manikumar.reddy@gmail.com>

Closes #7530 from omkreddy/2.4-upgrade-docs

Chasego/kafka,guozhangwang/kafka,noslowerdna/kafka,apache/kafka,sslavic/kafka,lindong28/kafka,Chasego/kafka,TiVo/kafka,noslowerdna/kafka,sslavic/kafka,lindong28/kafka,Chasego/kafka,apache/kafka,TiVo/kafka,apache/kafka,guozhangwang/kafka,apache/kafka,lindong28/kafka,noslowerdna/kafka,TiVo/kafka,sslavic/kafka,Chasego/kafka,TiVo/kafka,guozhangwang/kafka,guozhangwang/kafka,sslavic/kafka,lindong28/kafka,noslowerdna/kafka