Incorrect JMX MBean name on Kafka doc page

[Andrew Otto]

In http://kafka.apache.org/documentation.html#monitoring, 

ISR expansion rate      
"kafka.server":name="ISRShrinksPerSec",type="ReplicaManager"    See above


I believe this should be 

"kafka.server":name="IsrExpandsPerSec",type="ReplicaManager"


-Andrew Otto