fix(actionlint): restore runners-privilegedescalation custom label (PRI-1736)

runners-privilegedescalation runners are decommissioned. Revert the
actionlint config back to empty labels and migrate renovate.yaml to
ubuntu-latest so actionlint passes and the workflow can still run.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/actionlint.yaml

@@ -1,3 +1,2 @@
 self-hosted-runner:
-  labels:
-    - runners-privilegedescalation
+  labels: []

.github/workflows/renovate.yaml

@@ -7,7 +7,7 @@ on:
 
 jobs:
   renovate:
-    runs-on: runners-privilegedescalation
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
         uses: actions/checkout@v6