docs: Update redis_chat_message_history.ipynb (#16344)
## Problem
Spent several hours trying to figure out how to pass
`RedisChatMessageHistory` as a `GetSessionHistoryCallable` with a
different REDIS hostname. This example kept connecting to
`redis://localhost:6379`, but I wanted to connect to a server not hosted
locally.
## Cause
Assumption the user knows how to implement `BaseChatMessageHistory` and
`GetSessionHistoryCallable`
## Solution
Update documentation to show how to explicitly set the REDIS hostname
using a lambda function much like the MongoDB and SQLite examples.
