Use ubuntu-slim for merge workflow

Author: josh

.github/workflows/merge.yml

@@ -8,7 +8,7 @@ permissions:
 
 jobs:
   merge:
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-slim
     if: github.actor == 'dependabot[bot]' && github.repository == 'josh/github_exporter'
 
     steps: