@DirtyCheck for abstract classes inherited by domains mentioned only in upgrade notes

The section that explains the changes in default dirty checking and @DirtyCheck usage for abstract classes inherited by domain classes for GORM 6.1.x is given only in [upgrade notes](http://gorm.grails.org/6.1.x/hibernate/manual/#upgradeNotes) but there are no corresponding changes in the [5.3. Inheritance in GORM](http://gorm.grails.org/6.1.x/hibernate/manual/#inheritanceInGORM) section.

This small inconsistency caused some struggle and research.

Thanks in advance.

Compare the GORM 6.1.x upgrade notes with the 5.3 Inheritance in GORM section linked in the issue, focusing on @DirtyCheck for abstract classes inherited by domain classes. Update the inheritance documentation so it covers the same behavior and usage described in the upgrade notes.

Written by the indexing model from the issue text.