ci: remove stale workflow

.github/workflows/stale.yaml

@@ -1,14 +0,0 @@
-name: 'Close stale issues and PRs'
-on:
-  schedule:
-    - cron: '30 1 * * *'
-
-jobs:
-  stale:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/stale@v9
-        with:
-          stale-issue-message: 'This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days.'
-          days-before-stale: 360
-          days-before-close: 30