* lisp/completion-preview.el (completion-preview-insert)
(completion-preview-insert-word)
(completion-preview-insert-sexp)
(completion-preview-complete)
(completion-preview-prev-candidate)
(completion-preview-next-candidate): Use 'interactive' to
associate command with 'completion-preview-active-mode'
instead of using a bespoke 'completion-predicate' property.
(completion-preview-active-p): Declare obsolete.