jenkins: fix typo

tests/gadget-zero/Jenkinsfile

@@ -12,7 +12,7 @@ pipeline {
                 sh "echo karl we are building $pr_from_sha"
                 checkout([$class: 'GitSCM', branches: [[name: "$pr_from_sha"]], userRemoteConfigs: [[url: "$pr_from_git_url"]]])
                 step([
-                    class: "GitHubCommitStatusSetter",
+                    $class: "GitHubCommitStatusSetter",
                     commitShaSource: [$class: "ManuallyEnteredShaSource", sha: "$pr_from_sha"],
                     reposSource: [$class: "ManuallyEnteredRepositorySource", url: "$pr_from_git_url"],
                     contextSource: [$class: "DefaultCommitContextSource"],