Checkmk Werk 15562: Drop unsupported distros

ID: 15562 Title: Drop unsupported distros Component: Site Management Level: 1 Class: Bug fix Version: 2.3.0b1 This change may affect you in case you've been using Checkmk with the following distros: <ul> <li>Ubuntu 16.04</li> <li>Ubuntu 18.04</li> <li>SLES 12 SP3</li> <li>SLES 12 SP4</li> <li>SLES 15</li> </ul> Checkmk will now not be built anymore for those distros.