[REG] Documentation no longer shows the relationship between classes from different modules

Compare the top table of:

• https://doc.qt.io/qt-5.9/qobject.html (good)
• https://doc.qt.io/qt-5.12/qobject.html (bad)

Newer versions of Qt have lost the "Instantiated By:" field. The "Inherited By:" list is also much shorter, only showing classes from Qt Core.

Updated 2020-09-19: Re-opening this issue as it is still partially present in Qt 5.15.1.

It looks like the QObject page is now fixed, but other pages are still affected:

• https://doc.qt.io/qt-5.9/qabstracttablemodel.html lists "Inherited By: QSqlQueryModel"
• https://doc.qt.io/qt-5/qabstracttablemodel.html lists nothing

• https://doc.qt.io/qt-5.9/qpagedpaintdevice.html lists "Inherited By: QPdfWriter and QPrinter"
• https://doc.qt.io/qt-5/qpagedpaintdevice.html lists "Inherited By: QPdfWriter" only