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 $) :

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

composer require <package-name>

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

Reopening in case something is decided by the Symfony doc team (since it's an ongoing discussion from what I understood).
In the meantime this will be released so users will have the symfony doc interface that allows easy copying.