bump stale to v8 too

.github/workflows/stale.yml

@@ -6,7 +6,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v4
+      - uses: actions/stale@v8
         with:
           stale-issue-message: 'This issue is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 7 days.'
           days-before-stale: 90