chore(docs): update example env file

.env.example

@@ -58,8 +58,10 @@ NONPROD_FORCE_SECURE=false
 LOG_CHANNEL=daily
 
 DB_CONNECTION=mysql
-DB_HOST=localhost
 DB_PORT=3306
+
+# Using docker? You don't need to set these, they're managed in docker-compose.yml.
+DB_HOST=localhost
 DB_DATABASE=laravel
 DB_USERNAME=root
 DB_PASSWORD=