[HttpFoundation] Remove deprecated Request::get() in favor of using properties

[alamirault]

Fix #21463

Request::get() was not documented, so I think there is no deprecation directive to add ?

[javiereguiluz]

Yes, we updated the docs in the past to use query, request, attributes, etc. instead of the get() method because that was the recommendation since a while ago. So, let's merge this. Thanks!