ci(dependabot_changelog_updater): add fields to enable new version of changelog updater (#1500)

All Submissions:

* [x] Have you followed the guidelines in our Contributing document?
* [x] Have you checked to ensure there aren't other open [Pull
Requests](https://github.com/fastly/cli/pulls) for the same
update/change?

Author: anthony-gomez-fastly

.github/workflows/dependabot_changelog_update.yml

@@ -23,6 +23,8 @@ jobs:
         uses: actions/checkout@v4
         with:
           token: ${{ steps.github-token.outputs.token }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          ref: ${{ github.event.pull_request.head.ref }}
       - name: Generate changelog entry
         uses: dangoslen/dependabot-changelog-helper@v4
         with: