Do not auto close "revived" issues.

We have an issue reviver (tools/github/reviver/) which revives issues that
still have pending TODOs remaining. Such revived issues are labeled with
"revived".

Currently the issue reviver workflow and stale workflow go in a loop closing
and re-opening issues every few months. Break this loop by not auto-closing
revived issues.

PiperOrigin-RevId: 624993203

.github/workflows/stale.yml

@@ -22,7 +22,7 @@ jobs:
         days-before-close: 90
         remove-stale-when-updated: true
         exempt-pr-labels: 'no-auto-close'
-        exempt-issue-labels: 'no-auto-close,type: enhancement,good first issue,status: help wanted,type: proposal'
+        exempt-issue-labels: 'no-auto-close,revived,type: enhancement,good first issue,status: help wanted,type: proposal'
         operations-per-run: 1000
         close-issue-label: 'auto-closed'
         close-pr-label: 'auto-closed'