Add note about replication in the transactions documentation

While developing locally, if the user creates a bucket with the defaults and creates a transaction with the defaults with will fail.

We need to add a note in the transactions documentation which says that during development you need to set replicas to 0 in your bucket otherwise your transactions won't be able to accomplish the default durability requirements.

https://docs.couchbase.com/java-sdk/3.0/howtos/distributed-acid-transactions-from-the-sdk.html