Exclude cla-signatures branch from stale branch deletion (#8319)

* Exclude cla-signatures branch from stale branch deletion

* improv: days before stale

Author: sestinj

.github/workflows/delete-stale-branches.yaml

@@ -17,6 +17,9 @@ jobs:
         uses: crs-k/[email protected]
         with:
           repo-token: "${{ secrets.GITHUB_TOKEN }}"
+          days-before-stale: 60
+          days-before-delete: 90
           pr-check: true
           dry-run: true
           ignore-issue-interaction: true
+          branches-filter-regex: "cla-signatures"