MINOR: Fix partition numbering from 0 to P-1 instead of P in docs (#8572)
MINOR: Fix partition numbering from 0 to P-1 instead of P in docs (#8572)

Small typo fix

Reviewers: Konstantine Karantasis <758382ce421b111ebd907baeb3652ad461358862@confluent.io>
lindong28/kafka,Chasego/kafka,TiVo/kafka,apache/kafka,sslavic/kafka,lindong28/kafka,TiVo/kafka,guozhangwang/kafka,TiVo/kafka,lindong28/kafka,sslavic/kafka,Chasego/kafka,lindong28/kafka,guozhangwang/kafka,TiVo/kafka,guozhangwang/kafka,guozhangwang/kafka,apache/kafka,sslavic/kafka,sslavic/kafka,apache/kafka,apache/kafka,Chasego/kafka,Chasego/kafka