Update docker.io/jenkins/jenkins Docker tag to v2.508

Dockerfile

@@ -1,6 +1,6 @@
 # Dockerfile
 # Jenkins LTS as of 2023-05-03
-FROM  docker.io/jenkins/jenkins:2.546-jdk21
+FROM  docker.io/jenkins/jenkins:2.508-jdk21
 
 USER root
 

renovate.json

@@ -1,18 +1,3 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
-  "platformAutomerge": true,
-  "packageRules": [
-    {
-      "matchUpdateTypes": [
-        "minor",
-        "patch",
-        "pin",
-        "digest"
-      ],
-      "ignoreTests": true,
-      "automerge": true,
-      "automergeType": "pr"
-    }
-  ]
-
 }