Get MTProxy/Public Service Announcement information
help.promoDataEmpty#98f6ac75 expires:int = help.PromoData;
help.promoData#8c39793f flags:# proxy:flags.0?true expires:int peer:Peer chats:Vector<Chat> users:Vector<User> psa_type:flags.1?string psa_message:flags.2?string = help.PromoData;
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help.getPromoData#c0977421 = help.PromoData;
This constructor does not require any parameters.