github-actions: bump actions/stale from 5 to 7 (#473)

Author: dependabot[bot]

.github/workflows/stale.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 90 days stale policy for issues & PRs
-        uses: actions/stale@v5
+        uses: actions/stale@v7
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           days-before-stale: 90