Imply mixed gender duel to mixed-sex combat (along with some other stuff)

BUR #35114 is pending approval.

create alias mixed-sex_combat -> mixed_gender_combat
create implication mixed_gender_duel -> mixed_gender_combat
create alias mixed-sex_duel -> mixed_gender_duel

Mixed gender duel is basically a 1v1 variant of the Mixed-sex combat. While the latter tag is almost completely comprised of 1v1 fight, I think it can be used as an umbrella tag for any mixed gender duel regardless of the number of participant.

So I think the tag "mixed-sex combat" should be re-aliased into "mixed gender combat" to avoid confusion with sex battle (i.e. a battle with sexual elements), then the tag "mixed gender duel" should be implied to mixed gender combat since it is a subset of it. Finally, adding "mixed-sex duel" as an alias for consistency.