net.c: remove unused HAVE_SIN6_SCOPE_ID_LINUX-based code

The AC_SIN6_SCOPE_ID autoconf macro that was able to define
HAVE_SIN6_SCOPE_ID_LINUX was removed by commit v4.4-98-g64f793a.

* net.c [HAVE_SIN6_SCOPE_ID_LINUX]: Remove.
1 file changed