bug#56823: 29.0.50; Inconsistent button size in NEWS

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Type C-h n RET to view NEWS, and then click on one of the buttons.
The big right arrow icon will be replaced by a smaller down arrow.

Both arrows are being displayed with the Symbola font.  It seems wrong
and unprofessional to place the size of our buttons at the mercy of the
user's symbol font.  I suggest making the default the XPM arrows used in
Custom instead.

In GNU Emacs 29.0.50 (build 88, x86_64-pc-linux-gnu)
 of 2022-07-29 built on trinity
Repository revision: 02b180e955ab0923b5fe2b8f362f1fedb092f760
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Fedora Linux 36 (Workstation Edition)

Configured using:
 'configure --with-x --with-x-toolkit=no --with-dumping=unexec
 --cache-file=/tmp/ccache --without-cairo'

Configured features:
ACL DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON LCMS2
LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NOTIFY INOTIFY OLDXMENU PNG RSVG
SECCOMP SOUND SQLITE3 THREADS TIFF UNEXEC WEBP X11 XDBE XFT XIM XINPUT2
XPM ZLIB

Important settings:
  value of $LANG: en_GB.UTF-8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: NEWS

Minor modes in effect:
  outline-minor-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  button-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search time-date subr-x mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils vc-git
diff-mode vc-dispatcher pcase emacs-news-mode noutline outline
easy-mmode icons cl-loaddefs cl-lib rmc iso-transl tooltip eldoc paren
electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel
term/x-win x-win term/common-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
faces cus-face macroexp files window text-properties overlay sha1 md5
base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting xinput2 x
multi-tty make-network-process emacs)

Memory information:
((conses 16 133002 9879)
 (symbols 48 21529 0)
 (strings 32 32182 2042)
 (string-bytes 1 843394)
 (vectors 16 18989)
 (vector-slots 8 571018 14987)
 (floats 8 63 103)
 (intervals 56 1476 785)
 (buffers 992 12))