ref(build): avoid using an external cache with Docker Build Cloud

.github/workflows/sub-build-docker-image.yml

@@ -120,6 +120,15 @@ jobs:
             type=edge,enable={{is_default_branch}}
             type=schedule
 
+      # Setup Docker Buildx to use Docker Build Cloud
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v3
+        with:
+          version: "lab:latest"
+          driver: cloud
+          endpoint: "zfnd/zebra"
+
       - name: Authenticate to Google Cloud
         id: auth
         uses: google-github-actions/auth@v2.1.2
@@ -146,15 +155,6 @@ jobs:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
-      # Setup Docker Buildx to use Docker Build Cloud
-      - name: Set up Docker Buildx
-        id: buildx
-        uses: docker/setup-buildx-action@v3
-        with:
-          version: "lab:latest"
-          driver: cloud
-          endpoint: "zfnd/zebra"
-
       # Build and push image to Google Artifact Registry, and possibly DockerHub
       - name: Build & push
         id: docker_build
@@ -174,17 +174,3 @@ jobs:
           # Don't read from the cache if the caller disabled it.
           # https://docs.docker.com/engine/reference/commandline/buildx_build/#options
           no-cache: ${{ inputs.no_cache }}
-          # To improve build speeds, for each branch we push an additional image to the registry,
-          # to be used as the caching layer, using the `max` caching mode.
-          #
-          # We use multiple cache sources to confirm a cache hit, starting from a per-branch cache.
-          # If there's no hit, we continue with a `main` branch cache, which helps us avoid
-          # rebuilding cargo-chef, most dependencies, and possibly some Zebra crates.
-          #
-          # The caches are tried in top-down order, the first available cache is used:
-          # https://github.com/moby/moby/pull/26839#issuecomment-277383550
-          cache-from: |
-            type=registry,ref=us-docker.pkg.dev/${{ vars.GCP_PROJECT }}/zebra-caching/${{ inputs.image_name }}${{ inputs.tag_suffix }}:${{ env.GITHUB_REF_SLUG_URL }}-cache
-            type=registry,ref=us-docker.pkg.dev/${{ vars.GCP_PROJECT }}/zebra-caching/${{ inputs.image_name }}${{ inputs.tag_suffix }}:main-cache
-          cache-to: |
-            type=registry,ref=us-docker.pkg.dev/${{ vars.GCP_PROJECT }}/zebra-caching/${{ inputs.image_name }}${{ inputs.tag_suffix }}:${{ env.GITHUB_REF_SLUG_URL }}-cache,mode=max