[ci] Do not stale issues/prs assigned to any milestone (SeleniumHQ#15259)

* [ci] Do not stale issues/prs assigned to any milestone
* Use config exempt-all-milestones

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Signed-off-by: Viet Nguyen Duc <[email protected]>
Co-authored-by: Viet Nguyen Duc <[email protected]>

Author: nvborisenko

.github/workflows/stale.yml

@@ -23,6 +23,7 @@ jobs:
           stale-issue-label: 'I-stale'
           days-before-stale: 180
           days-before-close: 14
+          exempt-all-milestones: true
       - uses: actions/stale@v9
         with:
           close-issue-message: 'This issue was closed because we did not receive any additional information after 14 days.'