bug#81560: 31.0.91; dframe-update-speed specifies :type integer

The speedbar uses the customizable variable `dframe-update-speed' to
check for updates. This variable has variable :type `integer' but
shorter delays are supported, e.g., 0.5. I suggest to change the
variable :type to `number'.

In GNU Emacs 31.0.91 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.49, cairo version 1.18.4) of 2026-07-30
Windowing system distributor 'The X.Org Foundation', version 11.0.12101016
System Description: Debian GNU/Linux 13 (trixie)

Configured using:
 'configure --prefix=$HOME/.local/share/emacs-install
 --without-compress-install --with-tree-sitter=ifavailable
 --with-native-compilation --with-dbus --without-selinux
 --without-threads --disable-gc-mark-trace --without-gsettings
 --without-gpm --with-cairo --with-cairo-xcb --with-xinput2
 --with-x-toolkit=gtk3 --without-toolkit-scroll-bars 'CFLAGS=-O3
 -mtune=native -march=native''

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS HARFBUZZ JPEG LIBOTF LIBSYSTEMD
LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP
SOUND SQLITE3 TIFF TREE_SITTER WEBP X11 XCOMPOSITE XDBE XFIXES XIM
XINERAMA XINPUT2 XPM XRANDR XRENDER XSHAPE XSYNC GTK3 ZLIB