story: update outdated diff types
/+ *story
!:
|_ tale=story
-+$ story-additions [entry-additions=story prose-additions=story]
-+$ story-deletions [entry-deletions=story prose-deletions=story]
-+$ story-diff [additions=story-additions deletions=story-deletions]
++$ story-diff [additions=story deletions=story]
::
++ grad
|%
