Core/Player: Set correct Gender by Modelid

An example: You are a blood elf female, you use [Iron Boot Flask], you turn into a male dwarf, you use  [Orb of the Sin'dorei] and it will turn you into a blood elf male. This is the correct behavior like retail.

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

@@ -14652,6 +14652,9 @@ bool Unit::IsPolymorphed() const
 void Unit::SetDisplayId(uint32 modelId)
 {
     SetUInt32Value(UNIT_FIELD_DISPLAYID, modelId);
+	// Set Gender by modelId
+	if (CreatureModelInfo const* minfo = sObjectMgr->GetCreatureModelInfo(modelId))
+		SetByteValue(UNIT_FIELD_BYTES_0, 2, minfo->gender);
 }
 
 void Unit::RestoreDisplayId()