Remove instructions on boot splash screens

They haven't worked for years in the way described, and following
further advice online to enable VESA results in an unbootable system!

It can be put back when vt(4) supports them.

PR:		kern/210432

documentation/content/en/books/handbook/boot/_index.adoc

@@ -52,7 +52,6 @@ After reading this chapter, you will recognize:
 
 * The components of the FreeBSD bootstrap system and how they interact.
 * The options that can be passed to the components in the FreeBSD bootstrap in order to control the boot process.
-* How to configure a customized boot splash screen.
 * The basics of setting device hints.
 * How to boot into single- and multi-user mode and how to properly shut down a FreeBSD system.
 
@@ -319,52 +318,6 @@ The resource configuration system reads in configuration defaults from [.filenam
 
 To learn more about the resource configuration system, refer to man:rc[8] and examine the scripts located in [.filename]#/etc/rc.d#.
 
-[[boot-splash]]
-== Configuring Boot Time Splash Screens
-
-Typically when a FreeBSD system boots, it displays its progress as a series of messages at the console. A boot splash screen creates an alternate boot screen that hides all of the boot probe and service startup messages. A few boot loader messages, including the boot options menu and a timed wait countdown prompt, are displayed at boot time, even when the splash screen is enabled. The display of the splash screen can be turned off by hitting any key on the keyboard during the boot process.
-
-There are two basic environments available in FreeBSD. The first is the default legacy virtual console command line environment. After the system finishes booting, a console login prompt is presented. The second environment is a configured graphical environment. Refer to crossref:x11[x11,The X Window System] for more information on how to install and configure a graphical display manager and a graphical login manager.
-
-Once the system has booted, the splash screen defaults to being a screen saver. After a time period of non-use, the splash screen will display and will cycle through steps of changing intensity of the image, from bright to very dark and over again. The configuration of the splash screen saver can be overridden by adding a `saver=` line to [.filename]#/etc/rc.conf#. Several built-in screen savers are available and described in man:splash[4]. The `saver=` option only applies to virtual consoles and has no effect on graphical display managers.
-
-By installing the package:sysutils/bsd-splash-changer[] package or port, a random splash image from a collection will display at boot. The splash screen function supports 256-colors in the bitmap ([.filename]#.bmp#), ZSoft PCX ([.filename]#.pcx#), or TheDraw ([.filename]#.bin#) formats. The [.filename]#.bmp#, [.filename]#.pcx#, or [.filename]#.bin# image has to be placed on the root partition, for example in [.filename]#/boot#. The splash image files must have a resolution of 320 by 200 pixels or less in order to work on standard VGA adapters. For the default boot display resolution of 256-colors and 320 by 200 pixels or less, add the following lines to [.filename]#/boot/loader.conf#. Replace _splash.bmp_ with the name of the bitmap file to use:
-
-[.programlisting]
-....
-splash_bmp_load="YES"
-bitmap_load="YES"
-bitmap_name="/boot/splash.bmp"
-....
-
-To use a PCX file instead of a bitmap file:
-
-[.programlisting]
-....
-splash_pcx_load="YES"
-bitmap_load="YES"
-bitmap_name="/boot/splash.pcx"
-....
-
-To instead use ASCII art in the https://en.wikipedia.org/wiki/TheDraw[https://en.wikipedia.org/wiki/TheDraw] format:
-
-[.programlisting]
-....
-splash_txt="YES"
-bitmap_load="YES"
-bitmap_name="/boot/splash.bin"
-....
-
-Other interesting [.filename]#loader.conf# options include:
-
-`beastie_disable="YES"`::
-This will stop the boot options menu from being displayed, but the timed wait count down prompt will still be present. Even with the display of the boot options menu disabled, entering an option selection at the timed wait count down prompt will enact the corresponding boot option.
-
-`loader_logo="beastie"`::
-This will replace the default words "FreeBSD", which are displayed to the right of the boot options menu, with the colored beastie logo.
-
-For more information, refer to man:splash[4], man:loader.conf[5], and man:vga[4].
-
 [[device-hints]]
 == Device Hints