package/netstat-nat: remove package
Fixes http://autobuild.buildroot.net/results/bc52c072121286ddde3eee98ac28feb98f33dbbd/
The package has not been updated in 15 years (since commit 60ce1b0842de
"Bump netstat-nat to 1.4.10"), the upstream URL is gone and the package
fails to build on modern gcc versions because of missing prototypes, so drop
it.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>