Fix: Dependabot branches may not push Docker images

Author: hoh

.github/workflows/build.yml

@@ -33,8 +33,8 @@ jobs:
 
       - name: Push the image to the cache
         # It's not possible to push packages from fork PRs.
-        if: github.ref == 'refs/heads/main' || github.event.pull_request.head.repo.full_name
-          == github.repository
+        if: (github.ref == 'refs/heads/main' || github.event.pull_request.head.repo.full_name
+          == github.repository) && github.actor != 'dependabot[bot]'
         run: |-
           docker tag pyaleph-node:${GITHUB_REF##*/} ghcr.io/$GITHUB_REPOSITORY/build-cache
           docker push ghcr.io/$GITHUB_REPOSITORY/build-cache