revert removal of ubunut EOL version

Author: Pearl1594

source/releasenotes/compat.rst

@@ -22,7 +22,7 @@ Supported OS Versions for Management Server
 This section lists the operating systems that are supported for running
 CloudStack Management Server.
 
--  Ubuntu 22.04 LTS, 24.04 LTS
+-  Ubuntu 20.04 LTS, 22.04 LTS, 24.04 LTS
 -  Oracle Linux 8, 9
 -  Alma Linux 8, 9
 -  Rocky Linux 8, 9
@@ -45,7 +45,7 @@ Supported Hypervisor Versions
 CloudStack supports three hypervisor families, KVM, XenServer/XCP-ng with XAPI,
 and VMware with vSphere.
 
--  Ubuntu 22.04 LTS, 24.04 LTS with KVM
+-  Ubuntu 20.04 LTS, 22.04 LTS, 24.04 LTS with KVM
 -  Oracle Linux 8, 9 with KVM
 -  Alma Linux 8, 9 with KVM
 -  Rocky Linux 8, 9 with KVM