Merge multiple "outdoor" tags

BUR #189 has been rejected.

create alias outdoors_sex -> outdoor_sex
create alias outdoor -> outdoors

4 tags combined into 2.

This bulk update request is pending automatic rejection in 5 days.

This bulk update request has been rejected because it was not approved within 45 days.

The bulk update request #189 (forum #15488) has been rejected by @DanbooruBot.