tools: configure never-stale label correctly

Feature requests are issues, not PRs.

PR-URL: nodejs#49498
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: targos

.github/workflows/close-stale-feature-requests.yml

@@ -48,7 +48,7 @@ jobs:
           close-issue-message: ${{ env.CLOSE_MESSAGE }}
           stale-issue-message: ${{ env.WARN_MESSAGE }}
           only-labels: feature request
-          exempt-pr-labels: never-stale
+          exempt-issue-labels: never-stale
           # max requests it will send per run to the GitHub API before it deliberately exits to avoid hitting API rate limits
           operations-per-run: 500
           remove-stale-when-updated: true