ci: pin SHA for dependabot/fetch-metadata

Author: Flashky

.github/workflows/automerge.yml

@@ -22,7 +22,7 @@ jobs:
     steps:
       - name: Metadata de Dependabot
         id: metadata
-        uses: dependabot/fetch-metadata@v2
+        uses: dependabot/fetch-metadata@08eff52bf64351f401fb50d4972fa95b9f2c2d1b #v2.4.0
         with:
           github-token: "${{ secrets.GITHUB_TOKEN }}"