deps: update actions/github-script action to v8 (#7192)

Co-authored-by: Blake Li <blakeli@google.com>

Author: renovate-bot

.github/workflows/approve-readme.yaml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.repository_owner == 'googleapis' && github.head_ref == 'autosynth-readme'
     steps:
-      - uses: actions/github-script@v7
+      - uses: actions/github-script@v8
         with:
           github-token: ${{secrets.YOSHI_APPROVER_TOKEN}}
           script: |