Address defcustom :type warnings

Address defcustom :type warnings

* lisp/calendar/diary-lib.el (diary-display-function):
* lisp/calendar/icalendar.el (icalendar-export-alarms):
* lisp/emacs-lisp/elint.el (elint-ignored-warnings):
* lisp/mail/sendmail.el (send-mail-function):
* lisp/net/gnutls.el (gnutls-verify-error):
* lisp/gnus/mm-decode.el (mm-text-html-renderer):
* lisp/gnus/message.el (message-send-mail-function): Fix misplaced
defcustom :tags (bug#66196).
(message-tool-bar): Remove duplicate, overwritten, and nonexistent
defcustom :type gmm-tool-bar-list-item.
* lisp/progmodes/idlwave.el (idlwave-begin-line-comment): Strip
excessive defcustom :type quoting.
* lisp/progmodes/ps-mode.el (ps-mode-paper-size): Consolidate paper
sizes with same dimensions into a single defcustom menu entry.
* lisp/textmodes/glyphless-mode.el (glyphless-mode-types): Remove
duplicate defcustom :type choice.