[chore] Allow way for PRs to never become stale (open-telemetry#1136)

Co-authored-by: Liudmila Molkova <limolkova@microsoft.com>

.github/workflows/stale-pr.yml

@@ -12,7 +12,7 @@ jobs:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           stale-pr-message: 'This PR was marked stale due to lack of activity. It will be closed in 7 days.'
           close-pr-message: 'Closed as inactive. Feel free to reopen if this PR is still being worked on.'
-          exempt-pr-labels: 'bug,work in progress,experts needed'
+          exempt-pr-labels: 'bug,work in progress,experts needed,never stale'
           exempt-draft-pr: true
           # opt out of defaults to avoid marking issues as stale
           days-before-stale: -1