ci: use ubuntu-slim for lint (#670)

Author: methane

.github/workflows/lint.yaml

@@ -8,7 +8,7 @@ jobs:
     # by the push to the branch.
     if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     steps:
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2