remove implication love_letter -> letter
I'm not really sure why this implication exists (other than because of the name) as most (if not all) forms of love letters will be in the shape of an envelope (with a heart on) and thus should not be tagged with letter, as far as I can understand. I also couldn't find any past discussion either for or against this implication, not even when it was made.
EDIT: The bulk update request #1914 (forum #153579) has been approved by @Hillside_Moose.
Updated by DanbooruBot