[!!!][BUGFIX] Don't override orphanRemoval setting from Doctrine
In Doctrine 2 ORM, orphanRemoval is disabled by default. In FLOW3 we want
orphanRemoval to happen, if the target is not an aggregate root, changing
the default Doctrine behavior.
Because we want developers to be able to override that override, we had a
check in place, to favor the setting coming from the annotation. But since
there is no way to check if the FALSE in the orphanRemoval of an annotation
is the default or has been explitly set, this would fail to allow an
override with FALSE.
For many-to-many we thus assume that orphanRemoval is very rarely a
useful thing, and thus skip our own default handling.
If you want orphanRemoval on many-to-many associations, you now must
explicitly enable it with the annotation option!