[Gameplay] Revitalize provides NEGATIVE healing on Mundo

Discovered during a game of ARAM. Mundo is constantly losing health from revitalize.

Observations: revitalize seem to INCREASE health costs, which means it may impact Mordekaiser as well.

The mastery kept gaining NEGATIVE healing score throughout the game, plummeting further the higher my health regen.

Steps to reproduce: pick the revitalize rune on mundo. Ravenous hunter was in my secondary slot, so that may or may not have an impact on this bug.