Rename housekeeping user

Use github-actions[bot] as suggested in actions/checkout#13 (comment)

Author: majk-p

.github/workflows/scala-steward.yml

@@ -15,5 +15,5 @@ jobs:
         uses: scala-steward-org/scala-steward-action@v2
         with:
           github-token: ${{ secrets.REPO_GITHUB_TOKEN }}
-          author-email: 12345+octocat@users.noreply.github.com
-          author-name: scala-steward
+          author-email: 41898282+github-actions[bot]@users.noreply.github.com
+          author-name: github-actions[bot]