libip6t_mh: Correct command to list named mh types in manpage

Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/extensions/libip6t_mh.man b/extensions/libip6t_mh.man
index 4559e78..8ec08c6 100644
--- a/extensions/libip6t_mh.man
+++ b/extensions/libip6t_mh.man
@@ -8,5 +8,5 @@
 .IR type
 or one of the MH type names shown by the command
 .nf
- ip6tables \-p ipv6\-mh \-h
+ ip6tables \-p mh \-h
 .fi