Update mysql_to_postgresql.md to deprecate these docs in favor of PGLoader
^ See Title. A client brought this up in a call, and I want to make it clear new docs are coming in 10.0.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
^ See Title. A client brought this up in a call, and I want to make it clear new docs are coming in 10.0.