ci: build for Fedora 39

Fedora 39 is out, so we need builds of *sshca-cli* for it.

ci/Jenkinsfile

@@ -9,6 +9,10 @@ pipeline {
                         name 'ARCH'
                         values 'amd64', 'arm64'
                     }
+                    axis {
+                        name 'FEDORA'
+                        values '38', '39'
+                    }
                 }
 
                 stages {
@@ -19,6 +23,10 @@ pipeline {
                                 yamlMergeStrategy merge()
                                 defaultContainer 'fedora'
                                 nodeSelector "kubernetes.io/arch=${ARCH}"
+                                containerTemplate {
+                                    name 'fedora'
+                                    image "registry.fedoraproject.org/fedora:${FEDORA}"
+                                }
                             }
                         }
                         environment {

ci/podTemplate.yaml

@@ -1,7 +1,6 @@
 spec:
   containers:
   - name: fedora
-    image: registry.fedoraproject.org/fedora:38
     command:
     - cat
     stdin: true