[repo] Update stale.yml - reduce days before stale to 450 (open-telemetry#5888)

Author: Timothy Mothra

.github/workflows/stale.yml

@@ -18,7 +18,7 @@ jobs:
           close-pr-message: 'Closed as inactive. Feel free to reopen if this PR is still being worked on.'
           operations-per-run: 400
           days-before-pr-stale: 7
-          days-before-issue-stale: 600
+          days-before-issue-stale: 450
           days-before-pr-close: 7
           days-before-issue-close: 7
           exempt-all-issue-milestones: true