docs: delete socks5-proxy sample

It is known to fail asserts and leak memory, making it not particularly
good as sample code.  Since we have relatively little interest in
maintaining this (especially now that we have the libuv guide and other
docs), it is clearer to delete it.

Refs: libuv#2414
Refs: libuv#1604
PR-URL: libuv#2605
Reviewed-By: Saúl Ibarra Corretgé <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

Author: vtjnash

Makefile.am

@@ -123,7 +123,6 @@ EXTRA_DIST = test/fixtures/empty_file \
              include \
              docs \
              img \
-             samples \
              android-configure-arm \
              android-configure-arm64 \
              android-configure-x86 \