Finish score/wakeMonster tidy (scoreSlot; drop unused return)

game/monsters.go

@@ -116,7 +116,7 @@ func (g *RogueGame) wanderer() {
 
 // wakeMonster is what to do when the hero steps next to a monster
 // (monsters.c wake_monster).
-func (g *RogueGame) wakeMonster(y, x int) *Monster {
+func (g *RogueGame) wakeMonster(y, x int) {
 	p := &g.Player
 
 	tp := g.Level.MonsterAt(y, x)
@@ -143,8 +143,6 @@ func (g *RogueGame) wakeMonster(y, x int) *Monster {
 			tp.Dest = &p.Pos
 		}
 	}
-
-	return tp
 }
 
 // meanWakes decides whether a sleeping mean monster starts the chase