workflow: stales: stop marking issues as stale automatically (#937)

While it's a good idea to automatically mark PR as stale when inactive,
we probably can live with inactive issues, or we can do a manual triage
from time to time. An issue can still be marked as 'stalled' by adding
the label manually, and will in turn be closed if no update is made
until the 'close' idle delay is reached.

Author: lumag

.github/workflows/stales.yml

@@ -19,6 +19,7 @@ jobs:
         exempt-pr-labels: bug,enhancement
         days-before-stale: 30
         days-before-close: 5
+        days-before-issue-close: -1
         remove-stale-when-updated: true
         remove-issue-stale-when-updated: true
         remove-pr-stale-when-updated: true