[Serializer] Name Converter

| Q                | A
| --------------- | ---
| Doc fix?      | no
| New docs? | yes symfony/symfony#13120
| Applies to   | 2.7

This is the documentation for the Serializer Name Converter feature.
missing semi-colon at the end of the line. I also believe using `str_replace('org_', '', $propertyName);` might make it more clear what this code is doing (and that's more important than the fastest code in doc examples imo)