Change: Use gender-neutral pronouns

src/graph_gui.cpp

@@ -1417,7 +1417,7 @@ struct PerformanceRatingDetailWindow : Window {
 		int64 needed = _score_info[score_type].needed;
 		int   score  = _score_info[score_type].score;
 
-		/* SCORE_TOTAL has his own rules ;) */
+		/* SCORE_TOTAL has its own rules ;) */
 		if (score_type == SCORE_TOTAL) {
 			for (ScoreID i = SCORE_BEGIN; i < SCORE_END; i++) score += _score_info[i].score;
 			needed = SCORE_MAX;