Synchronize invert flag order with manpages

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/extensions/libip6t_ipv6header.c b/extensions/libip6t_ipv6header.c
index 5597872..547f966 100644
--- a/extensions/libip6t_ipv6header.c
+++ b/extensions/libip6t_ipv6header.c
@@ -138,7 +138,7 @@
 {
 	printf(
 "ipv6header match options:\n"
-"--header [!] headers     Type of header to match, by name\n"
+"[!] --header headers     Type of header to match, by name\n"
 "                         names: hop,dst,route,frag,auth,esp,none,proto\n"
 "                    long names: hop-by-hop,ipv6-opts,ipv6-route,\n"
 "                                ipv6-frag,ah,esp,ipv6-nonxt,protocol\n"