Update renovatebot check runner to ubuntu 24.04

Author: jannebe

.github/workflows/check-renovatebot-config.yml

@@ -6,7 +6,7 @@ on:
 jobs:
   validate:
     name: Validate renovatebot config
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
         uses: actions/checkout@v3