Disable issue checking in stalebot (idaholab#20475)

This is based on discussion from one of the stalebot developers at: 
actions/stale#688

Also adjusts the PR message to contain our set days before stale and 
closure, for developer information.

.github/workflows/stale.yml

@@ -20,8 +20,9 @@ jobs:
     - uses: actions/stale@v5
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
-        stale-pr-message: 'This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.'
+        stale-pr-message: 'This pull request has been automatically marked as stale because it has not had recent activity in the last 30 days. It will be closed in 3 days if no further activity occurs. Thank you for your contributions.'
         stale-pr-label: 'stale'
         days-before-pr-stale: 30
         days-before-pr-close: 3
+        days-before-issue-stale: -1
         operations-per-run: 100