fix: correct permissions for vendor/cache files

Dockerfile

@@ -20,5 +20,5 @@ RUN /app/bootstrap-app-dir.sh
 USER nexus
 WORKDIR /app
 COPY --chown=nexus:nexus Gemfile Gemfile.lock ./
-COPY vendor/cache ./vendor/cache/
+COPY --chown=nexus:nexus vendor/cache ./vendor/cache/
 RUN /app/bootstrap-app-bundle.sh