Revert "ci(renovate): self-host Renovate + remove Dependabot"

This reverts commit abe3a46.

Author: Ahoo-Wang

.github/dependabot.yml

@@ -0,0 +1,15 @@
+version: 2
+updates:
+  - package-ecosystem: nuget
+    directory: /
+    schedule:
+      interval: weekly
+      day: monday
+    open-pull-requests-limit: 5
+
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+      day: monday
+    open-pull-requests-limit: 5

.github/workflows/renovate.yml

@@ -1,23 +1,5 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "extends": ["config:recommended"],
-  "timezone": "Asia/Shanghai",
-  "labels": ["dependencies"],
-  "commitMessagePrefix": "fix(deps)",
-  "commitMessageTopic": "{{depName}}",
-  "rangeStrategy": "bump",
-  "lockFileMaintenance": { "enabled": false },
-  "prConcurrentLimit": 5,
-  "packageRules": [
-    {
-      "description": "Group Spring ecosystem updates into a single PR",
-      "matchPackagePatterns": ["^org\\.springframework"],
-      "groupName": "spring"
-    },
-    {
-      "description": "Group Kotlin-related updates into a single PR",
-      "matchPackagePatterns": ["^org\\.jetbrains\\.kotlin"],
-      "groupName": "kotlin"
-    }
+  "extends": [
+    "config:base"
   ]
 }