refactor: use a variable for cloud builder

Author: fiam

.github/actions/buildpush/action.yaml

@@ -12,7 +12,6 @@ inputs:
   cloud_builder:
     description: "The cloud builder endpoint"
     required: false
-    default: "docker/collab-bu"
   docker_username:
     description: "Docker Hub username"
     required: true

.github/workflows/build.yaml

@@ -46,4 +46,5 @@ jobs:
           docker_username: ${{ vars.DOCKER_USERNAME }}
           docker_password: ${{ secrets.DOCKER_PASSWORD }}
           docker_hub_account: ${{ vars.DOCKER_HUB_ACCOUNT }}
+          cloud_builder: ${{ vars.CLOUD_BUILDER }}
           no-cache: ${{ inputs.no-cache }}

.github/workflows/ci.yaml

@@ -26,3 +26,4 @@ jobs:
           docker_username: ${{ vars.DOCKER_USERNAME }}
           docker_password: ${{ secrets.DOCKER_PASSWORD }}
           docker_hub_account: ${{ vars.DOCKER_HUB_ACCOUNT }}
+          cloud_builder: ${{ vars.CLOUD_BUILDER }}