ci: pin actions/stale to v9.1.0

Ticket: DO-14230

Author: therealdwright

.github/workflows/stale.yml

@@ -11,7 +11,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v4
+      - uses: actions/stale@5bef64f19d7facfb25b37b414482c7164d639639 #v9.1.0
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           stale-pr-message: 'This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 10 days.'