Avoid extra parenthesis in ruby code

Author: mlocati

README.md

@@ -56,7 +56,7 @@ To use the languages data generated from this tool you can use the `bin/export-p
 
 - `ruby`: build a ruby file that can be included
   ```bash
-  export-plural-rules --output=yourfile.rb ruby
+  export-plural-rules --parenthesis=no --output=yourfile.rb ruby
   ```
   Then you can use that generated file in your ruby scripts:
   ```ruby