Remove redundant requires of 'button'

Remove redundant requires of 'button'

* lisp/apropos.el:
* lisp/emacs-lisp/cl-print.el:
* lisp/emacs-lisp/debug.el:
* lisp/emacs-lisp/ert.el:
* lisp/emacs-lisp/shadow.el:
* lisp/facemenu.el:
* lisp/help-mode.el:
* lisp/man.el:
* lisp/progmodes/etags.el:
* lisp/textmodes/bibtex.el:
* lisp/woman.el: Don't require 'button'; it is preloaded since version
23.1.