github-actions: bump actions/github-script from 8.0.0 to 9.0.0 (openthread#13115)

Bumps [actions/github-script](https://github.com/actions/github-script) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/actions/github-script/releases)
- [Commits](actions/github-script@ed59741...3a2844b)

---
updated-dependencies:
- dependency-name: actions/github-script
  dependency-version: 9.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/size-report.yml

@@ -53,7 +53,7 @@ jobs:
         github-token: ${{ secrets.GITHUB_TOKEN }}
 
     - name: Post Report
-      uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd
+      uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3
       id: post-report
       with:
         script: |