Merge pull request matplotlib#25335 from rcomer/stale-typo

"Inactive" workflow: fix typo

Author: oscargus

.github/workflows/stale.yml

@@ -22,4 +22,4 @@ jobs:
           days-before-issue-close: 30
           ascending: true
           exempt-issue-labels: "keep"
-          exempt-pr-label: "keep,status: orphaned PR"
+          exempt-pr-labels: "keep,status: orphaned PR"