Update stale_issue.yml (#2880)

Add the auto label exemption label for PRs so they are not closed by the bot.

Author: kdaily

.github/workflows/stale_issue.yml

@@ -22,7 +22,7 @@ jobs:
         stale-issue-label: closing-soon
         exempt-issue-label: auto-label-exempt
         stale-pr-label: closing-soon
-        exempt-pr-label: pr/needs-review
+        exempt-pr-label: pr/needs-review,auto-label-exempt
         response-requested-label: response-requested
 
         # Don't set closed-for-staleness label to skip closing very old issues