First induction step of the completeness lemma for parse-repetition.
Theorem:
(defthm parse-repetition-when-tree-match-induction-step-1 (implies (and (mv-nth 0 (parse-element (mv-nth 2 (parse-?repeat input)))) (pred-element (mv-nth 2 (parse-?repeat input)))) (pred-repetition input)))