%setuid-programs was previously moved to be in the list sexp instead of just
the append one. This causes an "invalid G-expression input" error.
Error reported by: Kolev on #guix.
* doc/guix.texi (Setuid Programs): Move %setuid-programs out to the append
sexp.
Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>