userguide: minor correction for UserBuildConfig option for keymaps

[Adek336]

The following fixes the instruction on choosing a keymap through UserBuildConfig:

Index: docs/userguide/en/installation/install-source-linux.html
===================================================================
--- docs/userguide/en/installation/install-source-linux.html	(wersja 31397)
+++ docs/userguide/en/installation/install-source-linux.html	(kopia robocza)
@@ -112,7 +112,7 @@
 <pre># Add symlink/file (timezone and keymap settings) to the image.
 AddSymlinkToHaikuImage home config settings
 	: /boot/system/etc/timezones/Europe/Paris : timezone ;
-AddFilesToHaikuImage home config settings : German 
+AddFilesToHaikuImage home config settings : <keymap>German 
 	: Key_map ;</pre></li> 
 <li><p>The build process can be fine tuned until it fits your needs. You could create your own folder <span class="path">haiku/trunk/user_data/</span> and put files there that are then copied or unzipped into the image. Zipping is important when dealing with Haiku files and their attributes, because zipping them up will preserve them on non-BFS partitions.<br />
 For example:</p>

[humdinger]

Applied with hrev31428. Thanks!