build: fix broken stale issues workflow (#36843)

.github/workflows/stale.yml

@@ -24,6 +24,7 @@ jobs:
           exempt-issue-labels: "discussion,security \U0001F512,enhancement :sparkles:"
           only-pr-labels: not-a-real-label
   pending-repro:
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/stale@3de2653986ebd134983c79fe2be5d45cc3d9f4e1
         with: