fix card::is_can_be_special_summoned()

https://www.db.yugioh-card.com/yugiohdb/faq_search.action?ope=5&fid=8792&keyword=&tag=-1
https://yugioh-wiki.net/index.php?%C3%CF%C7%FB%BF%C0
Ｑ：フィールド上に地縛神が１体存在している時に、墓地の地縛神を《浅すぎた墓穴》で特殊召喚できますか？
Ａ：地縛神を対象に《浅すぎた墓穴》を発動できません。(16/09/26)

card.cpp

@@ -3164,7 +3164,7 @@ int32 card::is_can_be_special_summoned(effect* reason_effect, uint32 sumtype, ui
 	if((data.type & TYPE_PENDULUM) && current.location == LOCATION_EXTRA && (current.position & POS_FACEUP)
 		&& (sumtype == SUMMON_TYPE_FUSION || sumtype == SUMMON_TYPE_SYNCHRO || sumtype == SUMMON_TYPE_XYZ))
 		return FALSE;
-	if(((sumpos & POS_FACEDOWN) == 0) && pduel->game_field->check_unique_onfield(this, toplayer, LOCATION_MZONE))
+	if(pduel->game_field->check_unique_onfield(this, toplayer, LOCATION_MZONE))
 		return FALSE;
 	sumtype |= SUMMON_TYPE_SPECIAL;
 	if((sumplayer == 0 || sumplayer == 1) && !pduel->game_field->is_player_can_spsummon(reason_effect, sumtype, sumpos, sumplayer, toplayer, this))