Remove "male_only" tag as an alias to "male_focus"

Posted under Tags

The bulk update request #141 has been approved by @DontTouchMyCogs.

remove alias male_only -> male_focus

As the title says, I wish for these two tags to be separated. The similar tags "female_only" and "female_focus" are separated, so why are these two merged? There are a lot of pictures that have females in them but are tagged as "male_focus", but "male_only" implies there would be no presence of females. Please unalias these two.