UniqueIdSet.TryParse() no longer needs to make the parsed set read-only
UniqueIdSet.TryParse() no longer needs to make the parsed set read-only

dsbenghe/MailKit,matt2003/MailKit,sstraus/MailKit,jstedfast/MailKit,mganss/MailKit,jamie-dainton/MailKit,nachocove/MailKit,eino-makitalo/MailKit