[Documentation] Conditionally enable the bundle

[xabbuh]

Currently, the docs suggest to enable the bundle in the AppKernel as follows:

// ...
class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            // ...
            new EasyCorp\Bundle\EasyDeployBundle\EasyDeployBundle(),
        );

        // ...
    }

    // ...
}

However, doing so will break your application after deploying as the bundle will not be installed on your production environment (it's been installed as a dev dependency when following the installation instructions).