Move Docs Renovate configuration into top-level renovate.json. (#142)

* Move Docs Renovate configuration into top-level `renovate.json`.

In the same nature as 9ab276576b.

* [squash] w/ previous commit

Ref: 9ab276576b

docs/package.json

@@ -20,10 +20,5 @@
     "build": "chexo apollo-hexo-config -- generate",
     "clean": "hexo clean",
     "test": "npm run clean; npm run build"
-  },
-  "renovate": {
-    "extends": [
-      "apollo-docs"
-    ]
   }
 }

renovate.json

@@ -1,5 +1,8 @@
 {
-  "extends": [
-    "apollo-docs"
+  "pathRules": [
+    {
+      "paths": ["docs/package.json"],
+      "extends": ["apollo-docs"]
+    }
   ]
 }