ci: remove stale bot (#587)

.github/workflows/close_stale.yml

@@ -1,22 +0,0 @@
-name: Close inactive issues
-on:
-  schedule:
-    - cron: "30 1 * * *"
-
-jobs:
-  close-issues:
-    runs-on: ubuntu-latest
-    permissions:
-      issues: write
-    steps:
-      - uses: actions/stale@v8
-        with:
-          days-before-stale: 30
-          days-before-close: 14
-          stale-issue-label: "stale"
-          stale-issue-message: "This issue is stale because it has been open for 30 days with no activity."
-          close-issue-message: "This issue was closed because it has been inactive for 14 days since being marked as stale."
-          days-before-pr-stale: -1
-          days-before-pr-close: -1
-          exempt-all-assignees: true
-          repo-token: ${{ secrets.GITHUB_TOKEN }}