ruleset: do not emit redundant drop invalid rules

ruleset: do not emit redundant drop invalid rules

The wan interface drop rule unnecessarily persists when invalid state
is dropped globally and the rule cannot catch anything at all, so remove
it as the effect is achieved by default and to global extent.

Fixes: 119ee1a ("ruleset: drop ctstate invalid traffic for masq-enabled zones")
Signed-off-by: Andris PE <neandris@gmail.com>
[fix S-o-b tag, fix commit author, reword commit subject and message]
Signed-off-by: Jo-Philipp Wich <jo@mein.io>