remove $ so copy-to-clipboard works

[tacman]

No description provided.

[maelanleborgne]

We need to keep this $ sign because we're in the process of integrating the documentation to the symfony website. This will eventually render like so (then the selectionh won't take the $) :

[tacman]

Please re-consider, as the official documentation of Symfony suggests

composer require <package-name>

https://symfony.com/doc/current/bundles/best_practices.html