gha: remove CentOS 7 (EOL), add Ubuntu 24.04, use engine 26.1

- CentOS 7 reached EOL
- Adding Ubuntu 24.04 (LTS)
- Update the "old" engine version to install to 26.1

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

.github/workflows/ci.yml

@@ -11,10 +11,10 @@ jobs:
         os:
           - ubuntu:20.04
           - ubuntu:22.04
-          - centos:7
+          - ubuntu:24.04
           - quay.io/centos/centos:stream9
         version:
-          - "20.10"
+          - "26.1"
           - ""
 
     steps: