inheritance elaborate on sealed classes
inheritance elaborate on sealed classes

* inheritance elaborate on sealed classes

* Update languages/exercises/concept/inheritance/.docs/after.md

Co-authored-by: Erik Schierboom <6e321e24be838c7616721fdb824f9c65569cbfd8@hotmail.com>

Co-authored-by: Erik Schierboom <6e321e24be838c7616721fdb824f9c65569cbfd8@hotmail.com>

exercism/xcsharp,exercism/xcsharp