Core/Misc: Fix warning

Partially revert f0a742a8c4 to fix a warning about unhandled switch case (the same case that Coverity reported as dead code) .

src/server/game/Entities/Unit/Unit.cpp

@@ -15905,6 +15905,8 @@ void Unit::RemoveCharmedBy(Unit* charmer)
                     }
                 }
                 break;
+            case CHARM_TYPE_CONVERT:
+                break;
         }
     }