package/nginx: remove ipv6 option

Remove --with-ipv6 as this option does nothing since version 1.11.5 and
https://github.com/nginx/nginx/commit/2c84f7af2c97a55bf138a5fcedeb164733dc9bea

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/nginx/nginx.mk

@@ -14,8 +14,7 @@ NGINX_CONF_OPTS = \
 	--crossbuild=Linux::$(BR2_ARCH) \
 	--with-cc="$(TARGET_CC)" \
 	--with-cpp="$(TARGET_CC)" \
-	--with-ld-opt="$(TARGET_LDFLAGS)" \
-	--with-ipv6
+	--with-ld-opt="$(TARGET_LDFLAGS)"
 
 # www-data user and group are used for nginx. Because these user and group
 # are already set by buildroot, it is not necessary to redefine them.