Update actions/stale action to v9 (#2423)

Co-authored-by: elastic-renovate-prod[bot] <174716857+elastic-renovate-prod[bot]@users.noreply.github.com>

Author: elastic-renovate-prod[bot]

.github/workflows/stale.yml

@@ -8,7 +8,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@1160a2240286f5da8ec72b1c0816ce2481aabf84 # v8
+      - uses: actions/stale@28ca1036281a5e5922ead5184a1bbf96e5fc984e # v9
         with:
           stale-issue-label: stale
           stale-pr-label: stale