Remove SUSE Enterprise Linux 12 (jenkinsci#1564)

End of standard support 31 Oct 2024

https://www.suse.com/lifecycle/#product-suse-linux-enterprise-server

README.md

@@ -34,7 +34,6 @@ Labels commonly include operating system name, version, architecture, and Window
 | Red Hat Enterprise Linux 9 | `RedHatEnterprise` | `9.5`          | `amd64`      | // EOL: 31 May 2032
 | Rocky Linux 8              | `Rocky`            | `8.10`         | `amd64`      | // EOL: 31 May 2029
 | Rocky Linux 9              | `Rocky`            | `9.5`          | `amd64`      | // EOL: 31 May 2032
-| SLES 12                    | `SUSE`             | `12.5`         | `amd64`      | // EOL: 31 Oct 2027
 | SLES 15                    | `SUSE`             | `15`           | `amd64`      | // EOL: 31 Jul 2031
 | Ubuntu 20                  | `Ubuntu`           | `20.04`        | `amd64`      | // EOL:  2 Apr 2025
 | Ubuntu 22                  | `Ubuntu`           | `22.04`        | `amd64`      | // EOL:  1 Apr 2027
@@ -75,7 +74,7 @@ Red Hat Linux 9 and its derivatives intentionally do not deliver `lsb_release`.
 Red Hat Linux agents have another fallback based on `/etc/redhat-release`.
 
 Agents with an older version of SuSE Linux will fallback to `/etc/SuSE-release`. Older versions of this plugin might return "sles" or "SUSE LINUX" as OS name.
-This has been unified to "SUSE" as this is the lsb_release ID since 'SLES 12 SP2'.
+This has been unified to "SUSE".
 
 When `/etc/os-release` is used, less detailed labels may be provided because more specific version information is not included in the file.
 For example: