docs/manual/legal-notice.txt: update list of non-saved material

This list dates back to 2012. Since a long time now Buildroot saves the
patches applied as well as the actual source code for some external
toolchains. Update the manual accordingly.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit a74e57c932df5edd483ff43518fae4e931064d07)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/manual/legal-notice.txt

@@ -67,9 +67,8 @@ for packages released under BSD-like licenses, that you are not required to
 redistribute in source form.
 
 Moreover, due to technical limitations, Buildroot does not produce some
-material that you will or may need, such as the toolchain source code and the
-Buildroot source code itself (including patches to packages for which source
-distribution is required).
+material that you will or may need, such as the toolchain source code for
+some of the external toolchains and the Buildroot source code itself.
 When you run +make legal-info+, Buildroot produces warnings in the +README+
 file to inform you of relevant material that could not be saved.