qdoc: internal qmlabstract types in the "inherited by" list

Internal qmlabstract types should not be visible in the docs, but they do show up in "inherited by" lists. Consider the following inheritance hierarchy:

Control
 \_ Checkable (internal, qmlabstract)
     \_ CheckBox
      \_ Switch

Control is the base type of all controls. Checkable is an internal qmlabstract implementation detail, which is then inherited by various checkable controls such as CheckBox, and Switch.

The documentation for CheckBox and Switch shows correctly that they inherit Control, but the documentation for Control says incorrectly "inherited by Checkable" whereas it should say "inherited by CheckBox, Switch". A minimal test case attached.