Remove more or less inexact option concerning custom target skeleton

We discourage the addition of custom target skeleton into the official
Buildroot tree, so let's not encourage users to do this in the
documentation.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

docs/buildroot.html

@@ -346,10 +346,6 @@
       the contents of the skeleton are copied to output/target before
       any package installation.</li>
 
-      <li>Add support for your own target in Buildroot, so that you
-      have your own target skeleton (see <a href="#board_support">this
-      section</a> for details).</li>
-
       <li>In the Buildroot configuration, you can specify the path to a
       post-build script, that gets called <i>after</i> Buildroot builds all
       the selected software, but <i>before</i> the rootfs packages are