move standardrb to dev || test gemfile group

Gemfile

@@ -50,16 +50,16 @@ gem "bootsnap", require: false
 group :development, :test do
   # See https://guides.rubyonrails.org/debugging_rails_applications.html#debugging-with-the-debug-gem
   gem "debug", platforms: %i[ mri windows ]
+
+  # a linting tool, to encourage/enforce a consistent code style
+  gem "standardrb"
 end
 
 group :development do
   # Check for published security issues
   gem "bundler-audit"
 
   gem "pry", "~> 0.14.2"
-
-  # Add a linting command
-  gem "standardrb"
 
   # Use console on exceptions pages [https://github.com/rails/web-console]
   gem "web-console"