Add missing `env:`, tweak conditional

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

.github/workflows/stale.yml

@@ -32,8 +32,8 @@ jobs:
   remove_stale:
     # trigger "stale" removal immediately when stale issues are commented on
     # we need to explicitly check that the trigger does not run on comment on a PR as
-    # 'issue_comment' triggers on issues AND PR comments
-    if: github.event_name == 'issue_comment' && ${{ !github.event.issue.pull_request }}
+    # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#issue_comment-on-issues-only-or-pull-requests-only
+    if: ${{ !github.event.issue.pull_request && github.event_name != 'schedule' }}
     permissions:
       contents: read #  for actions/checkout
       issues: write #  to edit issues label
@@ -43,5 +43,6 @@ jobs:
         uses: actions/checkout@v3.5.2
       - name: Remove 'stale' label
         run: gh issue edit ${{ github.event.issue.number }} --remove-label ${{ env.stale_label }}
+        env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}