Remove empty line in README.md

Removed an empty line before the Infrastructure section.

README.md

 * [phpRedisAdmin](https://github.com/ErikDubbelboer/phpRedisAdmin) - A simple web interface to manage [Redis](https://redis.io/) databases.
 * [PHPSandbox](https://phpsandbox.io) - An online IDE for PHP in the browser.
 
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 ### Infrastructure
 *Infrastructure for providing PHP applications and services.*