(dolist (coding auto-coding-alist)
(when (and (string-match "[Aa][Rr][Cc]\\\\|" (car coding))
(eq (cdr coding) 'no-conversion))
(setcar coding (replace-match "" nil nil (car coding)))))
In my experience, the most important thing to remember when learning elisp is "C-h f", followed by "C-h i m elisp RET".