/topics/replication.md has a few naming/terminology issues

[stockholmux]

In pre-publishing review (#91), I found the following issue on /topics/replication.md

Since Redis OSS 4.0, all the sub-replicas will receive exactly the same replication stream from the master.

and

Before version 4.0, writable replicas were incapable of expiring keys with a time to live set.

We can remove the old versions.

We also need to update the language to use 'primary'.

[zuiderkwast]

We have just taken the decision to change master to primary. Until now, "master" is used consistently in the docs and in logging, error message, etc. from Valkey. I think we should do this change as a separate effort.

[zuiderkwast]

Removing the references to 4.0. For "master", refer to #148