feat(publick8s): upgrade to kubernetes 1.28 (#772)

As per
jenkins-infra/helpdesk#4144 (comment)

upgrading the publick8s kubernetes cluster and node pools to 1.28.9

Signed-off-by: jayfranco999 <jaideepfrancis999@gmail.com>

locals.tf

@@ -50,7 +50,7 @@ locals {
     "cijenkinsio_agents_1"      = "1.28.9"
     "infracijenkinsio_agents_1" = "1.28.9"
     "privatek8s"                = "1.28.9"
-    "publick8s"                 = "1.27.9"
+    "publick8s"                 = "1.28.9"
   }
 
   ci_jenkins_io_fqdn                 = "ci.jenkins.io"