Currently, we repeat the same info about upgrading from previous Zabbix versions in three places: Upgrade from sources, Uprade from packages RHEL , Upgrade from packages Debian

The table, in particular, has grown too long - this is not the best user experience we can offer. And duplicated info is harder to maintain.

Let's move all the duplicated information to the main Upgrade procedure page.

Each of the three pages mentioned above should remind users to check critical Changes between versions before upgrading.  Please esnure, that this reminder is highly visible.