Docs update for clarity on manual acknowledgement in batch consumers

[gvensan]

Request for docs update:

The batch consumer section could use some updates regarding acknowledgment.

Few pointers:

1. Throwing an exception would leave the messages unacknowledged and the messages would remain in the queue
2. A manual acknowledgment is at the level of the entire batch, not on the individual messages. Refer to the manual acknowledgment section for details.