Clarify Message in Setup Docker Env Script

[em-c-rod]

"SSL Certificate already exists. if you would like to regenerate your certificates, please delete the files in ./nginx/certs/ and re-run this script."

This language exists in setup-docker-env.sh, however, there is a .gitkeep file in that folder that should not be deleted when running locally. Suggest rewording the help message to be more clear.