Update README.md

Remove `phpDox`; it looks abandoned.

README.md

 * [APIGen](https://github.com/apigen/apigen) - Another API documentation generator.
 * [daux.io](https://github.com/dauxio/daux.io) - A documentation generator that uses Markdown files.
 * [phpDocumentor](https://phpdoc.org/) - A documentation generator.
-* [phpDox](https://phpdox.net/) - A documentation generator for PHP projects (that is not limited to API documentation).
 * [Scramble](https://github.com/dedoc/scramble) - Automatically generates OpenAPI documentation from your code without annotations.
 * [zircote/swagger-php](https://github.com/zircote/swagger-php) - Generate OpenAPI documentation for your RESTful API.