ci: remove secrets guard that causes spurious 'no jobs' notifications

Author: jpr5

.github/workflows/notify-issue.yml

@@ -5,7 +5,6 @@ on:
 jobs:
   notify:
     runs-on: ubuntu-latest
-    if: ${{ secrets.SLACK_WEBHOOK != '' }}
     env:
       TITLE: ${{ github.event.issue.title }}
       URL: ${{ github.event.issue.html_url }}