Update buildkite plugin docker-compose to v3.0.3

Author: renovate-bot

.buildkite/pipeline.yml

@@ -2,5 +2,5 @@ steps:
   - name: ":golang:"
     command: "./scripts/test.sh"
     plugins:
-      - docker-compose#v3.0.2:
+      - docker-compose#v3.0.3:
           run: app