Update stale-bot.yml

Adding "operations-per-run: 90" to ensure the action catches all 600+ items that need to be processed etc.

If not defined, the default is 30 which captures only about 200 items a run which is not enough.

.github/workflows/stale-bot.yml

@@ -20,3 +20,4 @@ jobs:
           exempt-pr-labels: 'awaiting-approval,work-in-progress,enhancement,feature-request'
           exempt-issue-assignees: 'louislam'
           exempt-pr-assignees: 'louislam'
+          operations-per-run: 90