Allow composer install on Mautic 6.0.0

Hi, the plugin is yet to be enabled to be deployed with Mautic 6.0.0

```
pabloveintimilla/mautic-amazon-ses[v1.0.0, ..., v1.0.2] require mautic/core-lib ^5.0 -> found mautic/core-lib[5.0.0-alpha, ..., 5.x-dev] but it conflicts with your root composer.json require (~6.0.0)
```