Call public methods rather than class_eval'ing
Remove unused text? predicate method and delegation

The method has been removed in 09206716f8695f6b8467f15c1befa5a4c3c10978
(PR #16074), but the delegation was apparently missed, and one instance
of the method was added back with the addition of OID::Xml in
336be2bdf7dfa1b31879d0ab27e5f3101b351923 (PR #16072), so we can safely
rm both.