ci: fix merge-conflict-autolabel Github Action (#483)

Author: raphodn

.github/workflows/auto-assign-pr.yml

@@ -10,6 +10,6 @@ permissions:
 
 jobs:
   assign-author:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     steps:
       - uses: toshimaru/auto-author-assign@v2.1.1