Remove unnecessary fields from renovate configuration for GitHub Actions

Author: linuxdaemon

.github/renovate.json

@@ -1,16 +1,12 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": ["config:base"],
-  "platform": "github",
   "labels": ["update"],
   "prConcurrentLimit": 5,
   "packageRules": [
     {
       "matchManagers": ["github-actions"],
-      "pinDigests": true,
-      "commitMessageTopic": "github-actions",
-      "groupName": "github-actions",
-      "automerge": false
+      "pinDigests": true
     }
   ]
 }