PS-10190 [DOCS] - Binary Log UDFs functions documentation incomplete 8.4

[patrickbirch]

modified:   docs/binlogging-replication-improvements.md

[percona-ysorokin]

@patrickbirch @alina-derkach-oaza
You don't really need to apply CAST() everywhere.
See this comment https://perconadev.atlassian.net/browse/PS-10187?focusedCommentId=429566
In other words, you can still use CAST() and it will work but there is an easier alternative with just configuring your MySQL client.