Update actions/github-script action to v8

Author: renovate[bot]

.github/workflows/sign-off.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check PR for sign-off text
-        uses: actions/github-script@v7
+        uses: actions/github-script@v8
         with:
           script: |
             // We don't require owners or members of the org to sign off.