chore: undo Renovate fixture bump experiment (#511)

Reverting netlify/next-runtime-minimal#487 and netlify/next-runtime-minimal#499.

We've learned what we needed to.

renovate.json

@@ -1,16 +1,4 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "extends": ["local>netlify/renovate-config"],
-  "ignorePaths": ["**/node_modules/**"],
-  "packageRules": [
-    {
-      "description": "Stable & unstable Next.js bumps in test fixtures (no automerge)",
-      "matchFileNames": ["tests/**/fixtures/**/package.json"],
-      "matchPackageNames": ["next"],
-      "ignoreUnstable": false,
-      "labels": ["bump-framework-in-fixtures", "run-e2e-tests"],
-      "schedule": null,
-      "automerge": false
-    }
-  ]
+  "extends": ["local>netlify/renovate-config"]
 }