style: docker lint

Dockerfile

 FROM ruby:2.7.5-slim-bullseye
 
 # Bootstrap scripts will also be used by stage 2 (rails-runtime-base-image).
-ADD /app/bootstrap*sh /app/
+COPY /app/bootstrap*sh /app/
 RUN chmod +x /app/bootstrap*sh
 
 # Install OS packages required for the gem build environment.