MINOR: docs typo in '--zookeeper myhost:2181--execute'
MINOR: docs typo in '--zookeeper myhost:2181--execute'

this PR will fix a typo related to docs:
http://kafka.apache.org/21/documentation.html#rep-throttle

```bash
$ bin/kafka-reassign-partitions.sh --zookeeper myhost:2181--execute --reassignment-json-file bigger-cluster.json —throttle 50000000
```

I think `myhost:2181` should be `localhost:2181` and followed by a `space`

Author: opera443399 <pc@pcswo.com>

Reviewers: Gwen Shapira

Closes #6704 from opera443399/docs-ops-typo

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