Update dependabot/fetch-metadata to v3.0.0 for Node 24 compatibility

Author: alexdlaird

.github/workflows/automerge.yml

@@ -21,7 +21,7 @@ jobs:
     if: github.actor == 'dependabot[bot]'
     steps:
       - name: Get Dependabot metadata
-        uses: dependabot/fetch-metadata@v2
+        uses: dependabot/fetch-metadata@v3.0.0
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
       - name: Enable auto-merge